IE8 是否支持 javascript .map() 函数？
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Is the javascript .map() function supported in IE8?
提问by Richard H
When doing this:
这样做时：
var a = new Array("a", "b");
a.map(function() { });
in IE8 I get:
在 IE8 中我得到：
"Object doesn't support this property or method"
Is this method not supported in IE8, or do I have some other problem? I've had a Google, but get lots of Google Maps javascript issues/questions...
IE8 不支持此方法，还是我有其他问题？我有一个谷歌，但有很多谷歌地图 javascript 问题/问题......
Edit: OK so IE8 and below DO NOT support the .map() function. Copy-paste the code from MDN herewhich will add the .map() function to the Array prototype exactly per the specs if not natively supported (and it seems to work perfectly).
编辑：好的，所以 IE8 及以下不支持 .map() 函数。将 MDN 中的代码复制粘贴到此处，如果本机不支持，它将完全按照规范将 .map() 函数添加到 Array 原型中（并且它似乎工作得很好）。
回答by Interactive Tribe
The solution is jQuery.map
解决方案是 jQuery.map
Instead of this:
a.map(function( ) { });
取而代之的是：
a.map(function( ) { });
You have to do
你必须要做
jQuery.map(a, function( ) {
//what ever you want todo ..
}
jQuery.map(a, function( ) {
//what ever you want todo ..
}
回答by Justin Niessner
回答by Harry
(function(fn){
if (!fn.map) fn.map=function(f){var r=[];for(var i=0;i<this.length;i++)r.push(f(this[i]));return r}
if (!fn.filter) fn.filter=function(f){var r=[];for(var i=0;i<this.length;i++)if(f(this[i]))r.push(this[i]);return r}
})(Array.prototype);
Put anywhere before first .map or .filter call. Problem solved. jQuery.map() method doesn't work as expected.
放在第一个 .map 或 .filter 调用之前的任何位置。问题解决了。jQuery.map() 方法无法按预期工作。
UPDATE:I've just tested it on sparse arrays: if map or filter argument is a function which accepts and handles undefinedvalue - it works, but the results are not obvious:
更新：我刚刚在稀疏数组上对其进行了测试：如果 map 或 filter 参数是一个接受和处理undefined值的函数- 它可以工作，但结果并不明显：
Let's define test sparse array:
让我们定义测试稀疏数组：
var t = []
t[1] = 1; t[3] = 3; t[5] = 5;
Let's see what does IE8 say about t: "[undefined, 1, undefined, 3, undefined, 5]"
来看看IE8对t是怎么说的：“[undefined, 1, undefined, 3, undefined, 5]”
Let's try:
咱们试试吧：
t.filter(function(x){return x<4})
What is it, IE8? It's: "[1, 3]". Note - no undefined values. I would personally expect that.
这是什么，IE8？它是："[1, 3]"。注意 - 没有未定义的值。我个人希望如此。
But try THIS:
但是试试这个：
t.map(function(x){return 2<<x})
And... "[2, 4, 2, 16, 2, 64]". That's weird! :) Try this:
还有... "[2, 4, 2, 16, 2, 64]"。这很奇怪！：） 尝试这个：
t.map(function(x){return Math.pow(2,x)})
And?... "[NaN, 2, NaN, 8, NaN, 32]"- I would rather expect this result for the previous test. It's at least logical - Math.pow() is supposed to return a numbertype, NaN, regardless of it's meaning IS a special numbertype reserved for invalid operations. So the result is more or less correct. It would be fully correct as mapresult if t remained a sparse array.
还有？... "[NaN, 2, NaN, 8, NaN, 32]"- 我宁愿期待上次测试的结果。这至少是合乎逻辑的 - Math.pow() 应该返回一个number类型, NaN，不管它的含义是number为无效操作保留的特殊类型。所以结果或多或少是正确的。map如果 t 仍然是一个稀疏数组，那么结果将是完全正确的。
So without further ado - ultimately correct version of mapand filtermethods:
所以不用多说 -最终正确的版本map和filter方法：
(function(fn){
if (!fn.map) fn.map=function(f){var r=[];for(var i=0;i<this.length;i++)if(this[i]!==undefined)r[i]=f(this[i]);return r}
if (!fn.filter) fn.filter=function(f){var r=[];for(var i=0;i<this.length;i++)if(this[i]!==undefined&&f(this[i]))r[i]=this[i];return r}
})(Array.prototype);
And the test:
和测试：
var t = []; t[1] = 1; t[3] = 3; t[5] = 5;
var t1 = t.map(function(x){return 2<<x});
var t2 = t.filter(function(x){return x<10});
console.debug(t);
console.debug(t1);
console.debug(t2);
Expected results:
预期成绩：
[object Array] [undefined, 1, undefined, 3, undefined, 5]
[object Array][undefined, 4, undefined, 16, undefined, 64]
[object Array][undefined, 1, undefined, 3, undefined, 5]
[对象数组] [未定义，1，未定义，3，未定义，5]
[对象数组][未定义，4，未定义，16，未定义，64]
[对象数组][未定义，1，未定义，3，未定义，5]
回答by Oleksandr Tsurika
在 MSDN 上，地图要求：不支持以下文档模式：Quirks、Internet Explorer 6 标准、Internet Explorer 7 标准、Internet Explorer 8 标准。
Map is just a implementation of "Visitor" pattern for array. So easy substitute for it could be:
Map 只是数组的“访问者”模式的实现。如此简单的替代品可能是：
function visitArray(arr, visitor) {
var result = [];
for (var i = 0; i < arr.length; i ++) {
result[i] = visitor(arr[i]);
}
return result;
}
The function also takes array and function which to invoke on each array element. It returns a new array with result of visitor invokation for each original array element
该函数还采用数组和要在每个数组元素上调用的函数。它返回一个新数组，其中包含每个原始数组元素的访问者调用结果
