Array.prototype.filter()

  1 <!DOCTYPE html>
  2 <html>
  3 
  4     <head>
  5         <meta charset="UTF-8">
  6         <title></title>
  7     </head>
  8 
  9     <body>
 10         <script type="text/javascript">
 11             var words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];
 12 
 13             const result = words.filter(word => word.length > 6);
 14 
 15             console.log(result);
 16 
 17             function isBigEnough(value) {
 18                 if(value >= 10){
 19                     return true;//=== return value >=10
 20                 }
 21             }
 22 
 23             var filtered = [12, 5, 8, 130, 44].filter(isBigEnough);
 24             console.log(filtered)
 25             
 26             
 27             
 28             
 29             
 30             
 31             
 32             var fruits = ['apple', 'banana', 'grapes', 'mango', 'orange'];
 33 
 34 /**
 35  * Array filters items based on search criteria (query)
 36  */
 37 function filterItems(query) {
 38     //基于搜索的字母来从数组中找类似的选项
 39   return fruits.filter(function(el) {
 40       return el.toLowerCase().indexOf(query.toLowerCase()) > -1;
 41   })
 42 }
 43 
 44 console.log(filterItems('ap')); // ['apple', 'grapes']
 45 console.log(filterItems('an')); // ['banana', 'mango', 'orange']
 46 
 47 
 48 const fruits1 = ['apple', 'banana', 'grapes', 'mango', 'orange'];
 49 
 50 /**
 51  * Array filters items based on search criteria (query)
 52  */
 53 const filterItems1 = (query) => {
 54     //箭头函数的写法
 55   return fruits1.filter(el => el.toLowerCase().indexOf(query.toLowerCase()) > -1);
 56 };
 57 
 58 console.log(filterItems1('ap')); // ['apple', 'grapes']
 59 console.log(filterItems1('an')); // ['banana', 'mango', 'orange']
 60 
 61 
 62 
 63 
 64 
 65 
 66 
 67 if (!Array.prototype.filter){
 68   Array.prototype.filter = function(func, thisArg) {
 69     'use strict';
 70     if ( ! ((typeof func === 'Function' || typeof func === 'function') && this) )
 71         throw new TypeError();
 72    
 73     var len = this.length >>> 0,//因爲雖然這個 map 方法是在Array 的 prototype上的，
 74     //但實際上調用的時候，this 不一定是 Array類型，length不能得到保證，加上位運算後，可以將不確定的値轉換成Number。
 75         res = new Array(len), // preallocate array
 76         t = this, c = 0, i = -1;
 77     if (thisArg === undefined){
 78       while (++i !== len){
 79         // 检查是否设置了密钥
 80         if (i in this){
 81           if (func(t[i], i, t)){
 82             res[c++] = t[i];
 83           }
 84         }
 85       }
 86     }
 87     else{
 88       while (++i !== len){
 89         // 检查是否设置了密钥
 90         if (i in this){
 91           if (func.call(thisArg, t[i], i, t)){
 92             res[c++] = t[i];
 93           }
 94         }
 95       }
 96     }
 97    
 98     res.length = c; // 将数组缩小到适当的大小
 99     return res;
100   };
101 }
102         </script>
103     </body>
104 
105 </html>
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter 资料来自MDN