Why Does My Array Contains Function Always Return False, and How Can I Reliably Check for Values in JavaScript Arrays?

How to Check for Value in an Array

Determining whether a specific value exists in an array is a common programming task. However, when using the following custom function:

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

you may encounter unexpected behavior (always returning false). This is because the function relies on strict equality (==) comparisons, which can fail in certain cases (e.g., numbers that are considered equal but not identical).

A Robust Solution Using jQuery

For reliable value checks in arrays, consider using jQuery's utility function:

$.inArray(value, array)

This function searches the array for the specified value. If the value is found, it returns its index within the array. If the value is not found, it returns -1.

Example Usage

var arrValues = ["Sam","Great", "Sample", "High"];
var value = "Sam";

var result = $.inArray(value, arrValues);

if (result !== -1) {
    // Value found in array
} else {
    // Value not found in array
}

Additional References

• [How do I check if an array includes an object in JavaScript?](https://stackoverflow.com/questions/1232040/how-do-i-check-if-an-array-includes-an-object-in-javascript)

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