判断数组是否包含值 [英] Determine whether an array contains a value

问题描述

我需要确定一个值是否存在于数组中.

I need to determine if a value exists in an array.

我正在使用以下功能:

Array.prototype.contains = function(obj) {
    var i = this.length;
    while (i--) {
        if (this[i] == obj) {
            return true;
        }
    }
    return false;
}

上述函数总是返回false.

The above function always returns false.

数组值和函数调用如下:

The array values and the function call is as below:

arrValues = ["Sam","Great", "Sample", "High"]
alert(arrValues.contains("Sam"));

推荐答案

var contains = function(needle) {
    // Per spec, the way to identify NaN is that it is not equal to itself
    var findNaN = needle !== needle;
    var indexOf;

    if(!findNaN && typeof Array.prototype.indexOf === 'function') {
        indexOf = Array.prototype.indexOf;
    } else {
        indexOf = function(needle) {
            var i = -1, index = -1;

            for(i = 0; i < this.length; i++) {
                var item = this[i];

                if((findNaN && item !== item) || item === needle) {
                    index = i;
                    break;
                }
            }

            return index;
        };
    }

    return indexOf.call(this, needle) > -1;
};

你可以这样使用它:

var myArray = [0,1,2],
    needle = 1,
    index = contains.call(myArray, needle); // true

CodePen 验证/使用

这篇关于判断数组是否包含值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！