使用JavaScript从数组中过滤出数字索引
[英]Filtering out numeric indexes from an array with javascript
问题描述
This is the code i have written to filter out Numeric values from an array, but it is returning the complete array. 
这是我编写的用于从数组中滤除数值的代码，但它返回的是完整的数组。 I am not able to find out the problem in my code. 我无法在我的代码中找到问题。 Please help me i am stuck... 请帮助我，我被困住了...
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>html demo</title>
</head>
<body>
<script>
arr = ["apple", 5, "Mango", 6];
function filterNumeric(arrayName){
var i = 0;
var numericArray=[];
for (i; i <arrayName.length;i++){
if (typeof(arrayName[i] === 'number')) {
numericArray+=arrayName[i];
}
}
return numericArray;
}
var filter = filterNumeric(arr);
alert(filter);
</script>
</body>
</html>
2 个解决方案
解决方案1
1 已采纳 2014-09-16 09:24:22
Typo in the typeof check: 在typeof检查中输入：
if (typeof(arrayName[i]) === 'number') {
// ^^^ close the parentheses here
// ^^^ not there
解决方案2
1 2014-09-16 09:24:49
JavaScript arrays have a built-in filtering method : JavaScript数组具有内置的过滤方法 ：
var arr = ["apple", 5, "Mango", 6];
var filtered = arr.filter(function(item) { return (typeof item === "number")});
console.log(filtered); // Array [5,6]
As for your original code, beware that typeof is an operator, not a function, so 至于您的原始代码，请注意typeof是运算符，而不是函数，因此
if (typeof(foo === "whatever")) {
// ...
}
is equivalent to 相当于
if (typeof some_boolean_value) {
// ...
}
which evaluates to 评估为
if ("boolean") {
// ...
}
which will always be true, this is why you ended up with the whole content with no filtering whatsoever. 这将永远是正确的，这就是为什么您最终没有过滤就得到全部内容的原因。
Also note that the += operator is not overloaded for arrays, you will end up with a string concatenation of the remaining values: 还要注意，数组的+=运算符未重载，您将得到其余值的字符串连接：
var foo = [];
var bar = [1,2,3,4];
foo += bar[2];
console.log(foo); // "3"
console.log(typeof foo); // "string"
you must use the push method instead: 您必须改用push方法：
var foo = [];
var bar = [1,2,3,4];
foo.push(bar[2]);
console.log(foo); // Array [3]
console.log(typeof foo); // "object"
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