JavaScript

2018.08.25

indexの宣言がletかvarかで結果が変わる件を難しく書いた

jsらしい気がする。

const main = () => {
  const p = console.log;
  const copyFromBtoA = (a, b) => {
    for (const k of Object.keys(b)) {
      const v = b[k];
      a[k] = v;
    }
  };
  const getPromiseArr_let = () => {
    const ps = [];
    for (let i = 0; i < 5; i++) {
      ps.push(new Promise(resolve => {
        setTimeout(() => {
          resolve(i);
        }, 0);
      }));
    }
    return ps;
  };
  const getPromiseArr_var = () => {
    const ps = [];
    for (var i = 0; i < 5; i++) {
      ps.push(new Promise(resolve => {
        setTimeout(() => {
          resolve(i);
        }, 0);
      }));
    }
    return ps;
  };
  const doPromiseAll = (ps, func) => {
    Promise.all(ps).then(results => {
      func(results);
    });
  };
  const sub = () => {
    const psLet = [];
    const psVar = [];
    copyFromBtoA(psLet, getPromiseArr_let());
    copyFromBtoA(psVar, getPromiseArr_var());
    doPromiseAll(psLet, p);
    doPromiseAll(psVar, p);
  };
  sub();
};
main();

const main = () => {

const p = console.log;

const copyFromBtoA = (a, b) => {

for (const k of Object.keys(b)) {

const v = b[k];

a[k] = v;

}

};

const getPromiseArr_let = () => {

const ps = [];

for (let i = 0; i < 5; i++) {

ps.push(new Promise(resolve => {

setTimeout(() => {

resolve(i);

}, 0);

}));

}

return ps;

};

const getPromiseArr_var = () => {

const ps = [];

for (var i = 0; i < 5; i++) {

ps.push(new Promise(resolve => {

setTimeout(() => {

resolve(i);

}, 0);

}));

}

return ps;

};

const doPromiseAll = (ps, func) => {

Promise.all(ps).then(results => {

func(results);

});

};

const sub = () => {

const psLet = [];

const psVar = [];

copyFromBtoA(psLet, getPromiseArr_let());

copyFromBtoA(psVar, getPromiseArr_var());

doPromiseAll(psLet, p);

doPromiseAll(psVar, p);

};

sub();

};

main();

[ 0, 1, 2, 3, 4 ]
[ 5, 5, 5, 5, 5 ]

1 2	[ 0, 1, 2, 3, 4 ] [ 5, 5, 5, 5, 5 ]

2018.08.24

ループとコールバックの問題(varとletで結果が変わる)

非同期処理を実行するfor文で使うindexの宣言をvarでするかletでするかで、するかだけで結果が変わる。
こんなの難しすぎる。

const main_idxVar = () => {
  var ps = [];
  for (var i = 0; i < 5; i++) {
    ps.push(new Promise(resolve => {
      setTimeout(() => {
        resolve(i);
      }, 0);
    }));
  }
  Promise.all(ps).then(values => {
    console.log(values);
  });
};
const main_idxLet = () => {
  var ps = [];
  var len = 5;
  for (let i = 0; i < 5; i++) {
    ps.push(new Promise(resolve => {
      setTimeout(() => {
        resolve(i);
      }, 0);
    }));
  }
  Promise.all(ps).then(values => {
    console.log(values);
  });
};
main_idxVar();
main_idxLet();

const main_idxVar = () => {

var ps = [];

for (var i = 0; i < 5; i++) {

ps.push(new Promise(resolve => {

setTimeout(() => {

resolve(i);

}, 0);

}));

}

Promise.all(ps).then(values => {

console.log(values);

});

};

const main_idxLet = () => {

var ps = [];

var len = 5;

for (let i = 0; i < 5; i++) {

ps.push(new Promise(resolve => {

setTimeout(() => {

resolve(i);

}, 0);

}));

}

Promise.all(ps).then(values => {

console.log(values);

});

};

main_idxVar();

main_idxLet();

[ 5, 5, 5, 5, 5 ]
[ 0, 1, 2, 3, 4 ]

1 2	[ 5, 5, 5, 5, 5 ] [ 0, 1, 2, 3, 4 ]

2018.08.22

その年最初の落雷が起こった日の統計

1年間に平均12回雷が落ちる街がある。
1日あたりの落雷の発生確率を3.29%とすると、
その年最初の落雷が起こった日となる確率は、1月1日から数えて何日がいちばん高いか。

こたえ：1月1日

const p = console.log;
const probabilityOf = (percent) => {
  percent = Number(percent);
  if (Math.random() * 100 < percent) {
    return true;
  }
  return false;
};
const calcFirstDay = (percent) => {
  percent = Number(percent);
  if (percent <= 0) {
    p("invalid percent : " + percent);
    return -1;
  }
  let cnt = 0;
  while (true) {
    cnt++;
    if (probabilityOf(percent)) {
      return cnt;
    }
  }
};
const calcCntOfYear = (percent) => {
  let cnt = 0;
  for (let i = 0; i < 365; i++) {
    if (probabilityOf(percent)) {
      cnt++;
    }
  }
  return cnt;
};
const calcAverage = (a) => {
  let sum = 0;
  for (const n of a) {
    sum += n;
  }
  return sum / a.length;
};
const zeroPadding = (NUM, LEN) => {
  return (Array(LEN).join('0') + NUM).slice(-LEN);
};
const spacePadding = (NUM, LEN) => {
  return (Array(LEN).join(' ') + NUM).slice(-LEN);
};
const dispLine = (k, v, per = 1) => {
  let l = "";
  v = v * 1.0 / per;
  for (let i = 0; i < v; i++) {
    l += ".";
  }
  k = spacePadding(k, 3);
  p(k + " : " + l);
};
const dispChart = (a, per = 1) => {
  for (const k of Object.keys(a)) {
    const v = a[k];
    dispLine(k, v, per);
  }
};
const scoreFirstDay = [];
const percent = 3.29;
const times = 100000;
for (let i = 0; i < times; i++) {
  const fd = calcFirstDay(percent);
  if (scoreFirstDay[fd] === undefined) {
    scoreFirstDay[fd] = 1;
  } else {
    scoreFirstDay[fd] += 1;
  }
}

p("その年最初の落雷が起こった日の統計");
p();
p("1日あたりの落雷が起こる確率 : " + percent + "%");
p("観測年数 : " + times + "年");
p();
p("[日/年数(30分の1)]");

dispChart(scoreFirstDay, 30);

const p = console.log;

const probabilityOf = (percent) => {

percent = Number(percent);

if (Math.random() * 100 < percent) {

return true;

}

return false;

};

const calcFirstDay = (percent) => {

percent = Number(percent);

if (percent <= 0) {

p("invalid percent : " + percent);

return -1;

}

let cnt = 0;

while (true) {

cnt++;

if (probabilityOf(percent)) {

return cnt;

}

};

const calcCntOfYear = (percent) => {

let cnt = 0;

for (let i = 0; i < 365; i++) {

if (probabilityOf(percent)) {

cnt++;

}

return cnt;

};

const calcAverage = (a) => {

let sum = 0;

for (const n of a) {

sum += n;

}

return sum / a.length;

};

const zeroPadding = (NUM, LEN) => {

return (Array(LEN).join('0') + NUM).slice(-LEN);

};

const spacePadding = (NUM, LEN) => {

return (Array(LEN).join(' ') + NUM).slice(-LEN);

};

const dispLine = (k, v, per = 1) => {

let l = "";

v = v * 1.0 / per;

for (let i = 0; i < v; i++) {

l += ".";

}

k = spacePadding(k, 3);

p(k + " : " + l);

};

const dispChart = (a, per = 1) => {

for (const k of Object.keys(a)) {

const v = a[k];

dispLine(k, v, per);

}

};

const scoreFirstDay = [];

const percent = 3.29;

const times = 100000;

for (let i = 0; i < times; i++) {

const fd = calcFirstDay(percent);

if (scoreFirstDay[fd] === undefined) {

scoreFirstDay[fd] = 1;

} else {

scoreFirstDay[fd] += 1;

}

p("その年最初の落雷が起こった日の統計");

p();

p("1日あたりの落雷が起こる確率 : " + percent + "%");

p("観測年数 : " + times + "年");

p();

p("[日/年数(30分の1)]");

dispChart(scoreFirstDay, 30);

その年最初の落雷が起こった日の統計

1日あたりの落雷が起こる確率 : 3.29%
観測年数 : 100000年

[日/年数(30分の1)]
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  2 : ............................................................................................................
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その年最初の落雷が起こった日の統計

1日あたりの落雷が起こる確率 : 3.29%

観測年数 : 100000年

[日/年数(30分の1)]

1 : .............................................................................................................

2 : ............................................................................................................

3 : ........................................................................................................

4 : .......................................................................................................

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2018.08.19

ループとコールバックの問題(一応解決)

関数を外部で宣言しておくと期待通り動くらしい。

var ps = [];
var len = 5;

const metafunc = (func, arg) => {
    func(arg);
};

for(var i=0; i<len; i++){
    ps.push(new Promise(resolve => {
        setTimeout(
            metafunc(resolve, i),
            0
        );
    }));    
}
Promise.all(ps).then(results => {
    console.log(results)
});

var ps = [];

var len = 5;

const metafunc = (func, arg) => {

func(arg);

};

for(var i=0; i<len; i++){

ps.push(new Promise(resolve => {

setTimeout(

metafunc(resolve, i),

);

}));

}

Promise.all(ps).then(results => {

console.log(results)

});

[ 0, 1, 2, 3, 4 ]

1	[ 0, 1, 2, 3, 4 ]

2018.08.18

ループとコールバックの問題(未解決)

これ謎すぎる

var ps = [];
var len = 5;
for(var i=0; i<len; i++){
    ps.push(new Promise(resolve => {
        setTimeout(()=>{
            resolve(i);
        }, 0);
    }));    
}
Promise.all(ps).then(results => {
    console.log(results)
});

var ps = [];

var len = 5;

for(var i=0; i<len; i++){

ps.push(new Promise(resolve => {

setTimeout(()=>{

resolve(i);

}, 0);

}));

}

Promise.all(ps).then(results => {

console.log(results)

});

[ 5, 5, 5, 5, 5 ]

1	[ 5, 5, 5, 5, 5 ]

2018.08.08

keyを保持したままvalueでソート

javascriptはkeyが勝手に昇順ソートされる。
そういうことはしないで欲しい。

// (u.js)
'use strict';
module.exports = {
  p(a) {
    if(undefined === a){
      a = '';
    }
    console.log(a);
  },
  foreach(obj, func) {
    for (const key of Object.keys(obj)) {
      const value = obj[key];
      func(key, value);
    }
  },
  dispKeyValue(k, v) {
    console.log(k + " => " + v);
  },
  getRandomInt(min = 0, max = 9) {
    min = Number(min);
    max = Number(max);
    if (max <= min) {
      return max;
    }
    const randomOffset = Math.floor(Math.random() * (max - min + 1));
    return min + randomOffset;
  }
};

// (u.js)

'use strict';

module.exports = {

p(a) {

if(undefined === a){

a = '';

}

console.log(a);

foreach(obj, func) {

for (const key of Object.keys(obj)) {

const value = obj[key];

func(key, value);

}

dispKeyValue(k, v) {

console.log(k + " => " + v);

getRandomInt(min = 0, max = 9) {

min = Number(min);

max = Number(max);

if (max <= min) {

return max;

}

const randomOffset = Math.floor(Math.random() * (max - min + 1));

return min + randomOffset;

}

};

// (Main.js)
main();

function main() {
  'use strict';
  const u = require('./u');
  const swap = (a, l, r) => {
    const t = a[l];
    a[l] = a[r];
    a[r] = t;
  };
  const bubblesort = (a) => {
    const len = a.length;
    for (let i = 0; i < len - 1; i++) {
      for (let j = i + 1; j < len; j++) {
        if (a[j] < a[i]) {
          swap(a, i, j);
        }
      }
    }
  };
  const getKeyOfValue = (a, v) => {
    for (const key of Object.keys(a)) {
      const value = a[key];
      if (v === value) {
        return key;
      }
    }
    return null;
  };
  const getDeepCopy = (a) => {
    let b = [];
    for(const k of Object.keys(a)){
        const v = a[k];
        b[k] = v;
    }
    return b;
  };
  const deepCopy_fromAtoB = (a, b) => {
      u.foreach(b, (k, v) => {
        delete b[k];
      });
      
      u.foreach(a, (k, v) => {
          b[k] = v;
      });
  };
  const bubblesort_keepkey = (a) => {
    let b = getDeepCopy(a);
    bubblesort(b);
    let c = [];
    for (const v of b) {
      const key = getKeyOfValue(a, v);
      c['_' + key] = v;
    }
//    a = getDeepCopy(c);
    deepCopy_fromAtoB(c, a);
  };
  const sub = () => {
    const times = 1000000;
    const a = [];
    for (let i = 0; i < times; i++) {
      const n = u.getRandomInt(0, 10);
      if (undefined === a[n]) {
        a[n] = 1;
      } else {
        a[n] += 1;
      }
    }
    bubblesort_keepkey(a);
    u.foreach(a, u.dispKeyValue);
  };
  // 実質、main関数
  sub();
}

// (Main.js)

main();

function main() {

'use strict';

const u = require('./u');

const swap = (a, l, r) => {

const t = a[l];

a[l] = a[r];

a[r] = t;

};

const bubblesort = (a) => {

const len = a.length;

for (let i = 0; i < len - 1; i++) {

for (let j = i + 1; j < len; j++) {

if (a[j] < a[i]) {

swap(a, i, j);

}

};

const getKeyOfValue = (a, v) => {

for (const key of Object.keys(a)) {

const value = a[key];

if (v === value) {

return key;

}

return null;

};

const getDeepCopy = (a) => {

let b = [];

for(const k of Object.keys(a)){

const v = a[k];

b[k] = v;

}

return b;

};

const deepCopy_fromAtoB = (a, b) => {

u.foreach(b, (k, v) => {

delete b[k];

});

u.foreach(a, (k, v) => {

b[k] = v;

});

};

const bubblesort_keepkey = (a) => {

let b = getDeepCopy(a);

bubblesort(b);

let c = [];

for (const v of b) {

const key = getKeyOfValue(a, v);

c['_' + key] = v;

}

// a = getDeepCopy(c);

deepCopy_fromAtoB(c, a);

};

const sub = () => {

const times = 1000000;

const a = [];

for (let i = 0; i < times; i++) {

const n = u.getRandomInt(0, 10);

if (undefined === a[n]) {

a[n] = 1;

} else {

a[n] += 1;

}

bubblesort_keepkey(a);

u.foreach(a, u.dispKeyValue);

};

// 実質、main関数

sub();

}

_8 => 90527
_3 => 90615
_2 => 90618
_9 => 90679
_6 => 90697
_0 => 90701
_5 => 91005
_7 => 91153
_4 => 91288
_1 => 91310
_10 => 91407

_8 => 90527

_3 => 90615

_2 => 90618

_9 => 90679

_6 => 90697

_0 => 90701

_5 => 91005

_7 => 91153

_4 => 91288

_1 => 91310

_10 => 91407

2018.08.08

javascriptのコールバックとbind

// (u.js)
'use strict';
 
module.exports = {
    p(a) {
        console.log(a);
    },
    foreach(obj, func) {
        for (const key of Object.keys(obj)) {
            const value = obj[key];
            func(key, value);
        }
    },
    dispKeyValue(k, v) {
        this.p(k + " => " + v);
    }
};

// (u.js)

'use strict';

module.exports = {

p(a) {

console.log(a);

foreach(obj, func) {

for (const key of Object.keys(obj)) {

const value = obj[key];

func(key, value);

}

dispKeyValue(k, v) {

this.p(k + " => " + v);

}

};

// (main.js)
const u = require('./u');

const taro = {
  phrase: "こんにちは",
  name: "たろう",
  age: 19,
  greeting() {
    p(this.phrase + ", " + this.name + "(" + this.age + ")です。");
  },
};

// u.foreach(taro, u.dispKeyValue); // TypeError: Cannot read property 'p' of undefined
u.foreach(taro, u.dispKeyValue.bind(u));

// (main.js)

const u = require('./u');

const taro = {

phrase: "こんにちは",

name: "たろう",

age: 19,

greeting() {

p(this.phrase + ", " + this.name + "(" + this.age + ")です。");

};

// u.foreach(taro, u.dispKeyValue); // TypeError: Cannot read property 'p' of undefined

u.foreach(taro, u.dispKeyValue.bind(u));

phrase => こんにちは
name => たろう
age => 19
greeting => greeting() {
    p(this.phrase + ", " + this.name + "(" + this.age + ")です。");
  }

phrase => こんにちは

name => たろう

age => 19

greeting => greeting() {

p(this.phrase + ", " + this.name + "(" + this.age + ")です。");

}

2018.08.06

javascript(node.js)のライブラリを作る

練習がてら、安全とされるforeachの関数を作ってみた。
コールバック関数は毎回呼ばれるわけだから、
特定のkeyなりvalueなりを発見したらbreakまたはreturnするということができないので、
値を探すときには使えない。

// u.js
'use strict';

module.exports = {
    p: (a) => {
        console.log(a);
    },
    foreach: (obj, func) => {
        for (const key of Object.keys(obj)) {
            const value = obj[key];
            func(key, value);
        }
    }
}

// u.js

'use strict';

module.exports = {

p: (a) => {

console.log(a);

foreach: (obj, func) => {

for (const key of Object.keys(obj)) {

const value = obj[key];

func(key, value);

}

// main.js
const main = () => {
    'use strict';

    const u = require('./u');
    let taro = {
        phrase: "こんにちは",
        name: "たろう",
        age: 19,
        greeting(){
            p(this.phrase + ", " + this.name + "(" + this.age + ")です。");
        }
    };
    u.foreach(taro, (k, v) => {
        u.p(k + " : " + v);
        if(v === "たろう"){
            u.p("=== たろうを発見 ===");
            return;
        }
    });
}

main();

// main.js

const main = () => {

'use strict';

const u = require('./u');

let taro = {

phrase: "こんにちは",

name: "たろう",

age: 19,

greeting(){

p(this.phrase + ", " + this.name + "(" + this.age + ")です。");

}

};

u.foreach(taro, (k, v) => {

u.p(k + " : " + v);

if(v === "たろう"){

u.p("=== たろうを発見 ===");

return;

}

});

}

main();

$ node main.js
phrase : こんにちは
name : たろう
=== 発見 ===
age : 19
greeting : greeting(){
            p(this.phrase + ", " + this.name + "(" + this.age + ")です。");
        }

$ node main.js

phrase : こんにちは

name : たろう

=== 発見 ===

age : 19

greeting : greeting(){

p(this.phrase + ", " + this.name + "(" + this.age + ")です。");

}

2018.08.03

JavaScriptでカリー化

これ何が便利なのかわからん。

/*
カリー化 (currying, カリー化された=curried) とは、複数の引数をとる関数を、
引数が「もとの関数の最初の引数」で戻り値が
「もとの関数の残りの引数を取り結果を返す関数」
であるような関数にすること（あるいはその関数のこと）である。
*/
main();

function p(a){
    console.log(a);
}
function main(){
    var ret = sub(3, 5);
    p(ret);
    var ret = currySub(3)(5);
    p(ret);
}
function sub(a, b){
    return a - b;
}
function currySub(a){
    return function(b){
        return sub(a, b);
    };
}

カリー化 (currying, カリー化された=curried) とは、複数の引数をとる関数を、

引数が「もとの関数の最初の引数」で戻り値が

「もとの関数の残りの引数を取り結果を返す関数」

であるような関数にすること（あるいはその関数のこと）である。

main();

function p(a){

console.log(a);

}

function main(){

var ret = sub(3, 5);

p(ret);

var ret = currySub(3)(5);

p(ret);

}

function sub(a, b){

return a - b;

}

function currySub(a){

return function(b){

return sub(a, b);

};

}

-2
-2

-2

2018.06.30

オイラーとかゼータ関数とか

const PI = 3.14159265359;

function sum_zeta_2(n){
    var sum = 0;
    for(var i=1; i<=n; i++){
        sum += 1.0 / (i * i);
    }
    return sum;
}

function main(){
    console.log(sum_zeta_2(10000));
    console.log(PI * PI / 6.0);
}

main();

const PI = 3.14159265359;

function sum_zeta_2(n){

var sum = 0;

for(var i=1; i<=n; i++){

sum += 1.0 / (i * i);

}

return sum;

}

function main(){

console.log(sum_zeta_2(10000));

console.log(PI * PI / 6.0);

}

main();

1.6448340718480652
1.6449340668484431

1 2	1.6448340718480652 1.6449340668484431

5 6 7 8910 11 12

JavaScript

indexの宣言がletかvarかで結果が変わる件を難しく書いた

ループとコールバックの問題(varとletで結果が変わる)

その年最初の落雷が起こった日の統計

ループとコールバックの問題(一応解決)

ループとコールバックの問題(未解決)

keyを保持したままvalueでソート

javascriptのコールバックとbind

javascript(node.js)のライブラリを作る

JavaScriptでカリー化

オイラーとかゼータ関数とか

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