由于一些浏览器不提供标准的filter()函数,那么在javascript中怎样实现数组的过滤函数呢,望大牛指点
参考这个:
https://github.com/jashkenas/underscore/blob/master/underscore.js#L229
官方Array.filter()的polyfill:
if (!Array.prototype.filter) {
Array.prototype.filter = function(fun/*, thisArg*/) {
'use strict';
if (this === void 0 || this === null) {
throw new TypeError();
}
var t = Object(this);
var len = t.length >>> 0;
if (typeof fun !== 'function') {
throw new TypeError();
}
var res = [];
var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
for (var i = 0; i < len; i++) {
if (i in t) {
var val = t[i];
// NOTE: Technically this should Object.defineProperty at
// the next index, as push can be affected by
// properties on Object.prototype and Array.prototype.
// But that method's new, and collisions should be
// rare, so use the more-compatible alternative.
if (fun.call(thisArg, val, i, t)) {
res.push(val);
}
}
}
return res;
};
}
var arr = [3,5,6];
var newArr = arr.filter(function(v,i){
if(v>3){
return v;
}
});
//[5,6]
filter 是根据返回的值是否为真来判断是否保留元素,所以可以这样实现
Array.prototype.filter = Array.prototype.filter || function(func) {
var arr = this;
var r = [];
for (var i = 0; i < arr.length; i++) {
if (func(arr[i])) {
r.push(arr[i]);
}
}
return r;
}
因为目前大部分浏览器有 filter 实现,所以测试时只能改个名字叫 filterx,下面是测试代码
var data = [1,2,3,4,5,6,7];
Array.prototype.filterx = Array.prototype.filterx || function(func) {
var arr = this;
var r = [];
for (var i = 0; i < arr.length; i++) {
if (func(arr[i])) {
r.push(arr[i]);
}
}
return r;
}
console.log(data.filter(function(t) {
return t % 3 > 0;
}));
console.log(data.filterx(function(t) {
return t % 3 > 0;
}));