js中的拷贝和引用以及ES6大法好

一些简单的东西,被引用和拷贝坑了下。javascript

function *ngrams(sequence, n) {
  let  g = (function *(sequence){yield *sequence})(sequence);

  let history = [];
  while (n > 1) {
    history.push(g.next().value);
    n--;
  }
  for (let item of g) {
    history.push(item);
    // look at here.
    // yield Array.from(history); 
	yield history;
    history.shift();
  }
}

若是这时候用Array.from。。。WTF,什么鬼java

> Array.from(ngrams([1,2,3,4,5], 3));
[ [ 4, 5 ], [ 4, 5 ], [ 4, 5 ] ]

若是for of数组

> for (let w of ngrams([1,2,3,4,5], 3)){console.log(w);}
[ 1, 2, 3 ]
[ 2, 3, 4 ]
[ 3, 4, 5 ]

很怀疑Array.from干啥了。。。app

> Array.from(ngrams([1,2,3,4,5], 3), (v)=>{console.log(v)});
[ 1, 2, 3 ]
[ 2, 3, 4 ]
[ 3, 4, 5 ]
> Array.from(ngrams([1,2,3,4,5], 3), (v)=>v);
[ [ 4, 5 ], [ 4, 5 ], [ 4, 5 ] ]
> Array.from(ngrams([1,2,3,4,5], 3), (v)=>v+1);
[ '1,2,31', '2,3,41', '3,4,51' ]

这就明晰了,没想到会在js中碰到这种问题。。。ide

中午见有人讨论求一个数组最小值时这样:this

Math.min.apply(Object.create(null), [1,2,3]);code

说相比高程上说的方法,能更好防止变量污染。ip

因而去翻了翻spidermonkey和v8的实现,发现这个this根本就没用。。。至于apply,咱们如今有v8

Math.min(...[1,2,3]);it

ES6大法好啊。。。

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