在 Javascript 数组中查找元素
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Find element in Javascript Array
提问by djreed
Possible Duplicate:
Javascript - array.contains(obj)
What's wrong with this:
这有什么问题：
var zipCodes =(['90001','90002','90003']);
Test if the value exists in the array zipCodes
测试数组中是否存在该值 zipCodes
if('90001' in zipCodes) {
alert('True');
};
回答by user113716
The inoperator looks at property names, not values.
该in操作者查看属性的名称，而不是价值。
Because it's an Array, the property names will be the indices of the Array.
因为它是一个数组，属性名称将是数组的索引。
If you're only supporting a modern environment, you could use Array.prototype.indexOf().
如果您只支持现代环境，则可以使用Array.prototype.indexOf().
if(zipCodes.indexOf('90001') > -1) {
If you need to support environments that don't have .indexOf(), you could implement the MDN fix.
如果您需要支持没有 的环境.indexOf()，您可以实施MDN 修复。
if (!Array.prototype.indexOf) {
Array.prototype.indexOf = function (searchElement /*, fromIndex */ ) {
"use strict";
if (this === void 0 || this === null) throw new TypeError();
var t = Object(this);
var len = t.length >>> 0;
if (len === 0) return -1;
var n = 0;
if (arguments.length > 0) {
n = Number(arguments[1]);
if (n !== n) // shortcut for verifying if it's NaN
n = 0;
else if (n !== 0 && n !== (1 / 0) && n !== -(1 / 0)) n = (n > 0 || -1) * Math.floor(Math.abs(n));
}
if (n >= len) return -1;
var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);
for (; k < len; k++) {
if (k in t && t[k] === searchElement) return k;
}
return -1;
};
}
回答by Ben Simpson
If you want to check if the array contains a given value, you can use the indexOf method to check for the position of an item. If the item is not found in the array, a -1 is returned:
如果要检查数组是否包含给定值，可以使用 indexOf 方法检查项目的位置。如果在数组中找不到该项目，则返回 -1：
var zipCodes =(['90001','90002','90003']);
zipCodes.indexOf('90001') // 0
zipCodes.indexOf('90002') // 1
zipCodes.indexOf('90003') // 2
zipCodes.indexOf('90004') // -1
if(zipCodes.indexOf('90001') != -1) {
alert('True');
};
See more at http://freewebdesigntutorials.com/javaScriptTutorials/jsStringObject/indexOfMethod.htm
在http://freewebdesigntutorials.com/javaScriptTutorials/jsStringObject/indexOfMethod.htm查看更多
回答by jfriend00
Use an object instead. If this is all you're trying to do with the array, then an object is a much more efficient way to do a lookup list.
改用一个对象。如果这就是您试图对数组执行的全部操作，那么对象是一种更有效的查找列表方式。
var zipCodes = {"90001": true, "90002": true, "90003": true};
if ('90001' in zipCodes) {
alert('True');
}
jsfiddle here to see it work: http://jsfiddle.net/jfriend00/ZNGTq/
jsfiddle在这里看到它的工作：http: //jsfiddle.net/jfriend00/ZNGTq/
回答by PaulM
You need something like this:
你需要这样的东西：
var zipCodes =(['90001','90002','90003']);
if (zipCodes.has('90001')) {
....
}
Array.prototype.has=function(v){
for (i=0;i<this.length;i++){
if (this[i]==v) return i;
}
return false;
}
See this for more info:
请参阅此了解更多信息：
http://snook.ca/archives/javascript/testing_for_a_v
http://snook.ca/archives/javascript/testing_for_a_v
....
....
回答by Kon
Because inchecks for a property of an object. Check this out for converting "in object" to "in array": Testing for a Value in JavaScript Array
因为in检查对象的属性。看看这个将“in object”转换为“in array”： Testing for a Value in JavaScript Array
