Javascript – Check if all values of array are equal

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I need to find arrays where all values are equal. What's the fastest way to do this? Should I loop through it and just compare values?

['a', 'a', 'a', 'a'] // true
['a', 'a', 'b', 'a'] // false

Best Answer

const allEqual = arr => arr.every( v => v === arr[0] )
allEqual( [1,1,1,1] )  // true

Or one-liner:

[1,1,1,1].every( (val, i, arr) => val === arr[0] )   // true

Array.prototype.every (from MDN) : The every() method tests whether all elements in the array pass the test implemented by the provided function.

Related Solutions

Javascript – How to check if an element is hidden in jQuery

Since the question refers to a single element, this code might be more suitable:

// Checks CSS content for display:[none|block], ignores visibility:[true|false]
$(element).is(":visible");

// The same works with hidden
$(element).is(":hidden");

It is the same as twernt's suggestion, but applied to a single element; and it matches the algorithm recommended in the jQuery FAQ.

We use jQuery's is() to check the selected element with another element, selector or any jQuery object. This method traverses along the DOM elements to find a match, which satisfies the passed parameter. It will return true if there is a match, otherwise return false.

Javascript – How to convert a string to boolean in JavaScript

Do:

var isTrueSet = (myValue === 'true');

using the identity operator (===), which doesn't make any implicit type conversions when the compared variables have different types.

Don't:

You should probably be cautious about using these two methods for your specific needs:

var myBool = Boolean("false");  // == true

var myBool = !!"false";  // == true

Any string which isn't the empty string will evaluate to true by using them. Although they're the cleanest methods I can think of concerning to boolean conversion, I think they're not what you're looking for.

Best Answer

Related Solutions

Javascript – How to check if an element is hidden in jQuery

Javascript – How to convert a string to boolean in JavaScript

Do:

Don't:

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