CoffeeScriptで覚えたい文法

ワイ用のメモや

商の整数値

coffee

a // b

js

Math.floor(a / b)

整数化（切り捨て）

coffee

a // 1

js

Math.floor(a)

累乗

coffee

a ** b

js

Math.pow(a, b)

配列の走査

coffee

for value, key in array
   console.log key
   console.log value

js

var i, key, len, value;

for (key = i = 0, len = array.length; i < len; key = ++i) {
  value = array[key];
  console.log(key);
  console.log(value);
}

連想配列の走査

coffee

for key, value of hash
   console.log key
   console.log value

js

var key, value;

for (key in hash) {
  value = hash[key];
  console.log(key);
  console.log(value);
}

配列要素の指定

..は右端を含む
...は右端を含まない
点の数と意味の覚え方
..は「近い」ので「含む」。...は「遠い」ので「含まない」。
（@puriketu99談）

coffee

test = [0,1,2,3,4,5,6,7,8]

ika = test[0..3]
miman = test[0...3]

for i in [0..3]
   console.log i
for i in [0...3]
   console.log i

js

var i, ika, j, k, miman, test;

test = [0, 1, 2, 3, 4, 5, 6, 7, 8];

ika = test.slice(0, 4);

miman = test.slice(0, 3);

for (i = j = 0; j <= 3; i = ++j) {
  console.log(i);
}

for (i = k = 0; k < 3; i = ++k) {
  console.log(i);
}

スワップ

coffee

[theBait, theSwitch] = [theSwitch, theBait]

js

ref = [theSwitch, theBait], theBait = ref[0], theSwitch = ref[1];

いらん要素を捨てる

coffee

text = "Every literary critic believes he will
        outwit history and have the last word"
[first, ..., last] = text.split " "

js

var first, last, ref, text;

text = "Every literary critic believes he will outwit history and have the last word";

ref = text.split(" "), first = ref[0], last = ref[ref.length - 1];

比較演算子の連結

coffee

healthy = 200 > cholesterol > 60

js

healthy = (200 > cholesterol && cholesterol > 60);

ヒアドキュメント

"""で囲む
インデント入れてよし

coffee

text = """
       ora
       ora
       ora
       """

js

var text;

text = "ora\nora\nora";