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+---
+layout: page
+title: 2016年Js知识点
+categories: [笔记]
+tags: [2016,JS知识,个人,前端]
+---
+
+自己平时收集的JS小知识点。
+
+### 1. void 0
+```js
+   typeof void 0  		 //"undefined"
+   undefined === void 0  //true
+   undefined == void 0   //true
+   null == void 0        //true
+   "undefined" == void 0 //false
+```
+
+### 2. null
+`undefined` 表示未定义 ； `null`表示值为空。
+
+```js
+   typeof null         //"object"
+   undefined == null   //true
+   undefined === null  //false
+```
+
+### 3. 正负无穷大
+```js
+  Infinity //Infinity
+  1.7976931348623157E+1030899 //Infinity
+  -1.7976931348623157E+1030899 //-Infinity
+```
+
+### 4. Fisher-Yates shuffle 洗牌算法
+洗牌算法: [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
+
+```js
+  var shuffle = function(arr , n) {
+    if (n == null) n = Infinity;
+    var n = Math.max(Math.min(n, arr.length), 0);
+    var last = arr.length - 1;
+    for (var index = 0; index < n; index++) {
+      var rand = random(index, last);
+      var temp = arr[index];
+      arr[index] = arr[rand];
+      arr[rand] = temp;
+    }
+    return arr.slice(0, n);
+  };
+
+  var random = function(min, max) {
+    if (max == null) {
+      max = min;
+      min = 0;
+    }
+    return min + Math.floor(Math.random() * (max - min + 1));
+  };
+```