filter() method lets you test the entire array with an arbitrary criteria, and it returns a new array of all the matching items. If you need to return the first matching item, you’d use () instead of.

“The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.” - MDN Docs The most obvious alternative is (), but using () might save you future refactoring. Let result = needle.every(i => haystack.includes(i)) Ĭonsole.If you need to know if a JavaScript array contains an item, you have a couple of options other than just writing a for loop.

In this instance we replace some() with every() which evaluates true if all of the conditions are met. To query the array to match all of the values it is very similar. Let result = needle.some(i => haystack.includes(i)) Ĭonsole.log(result) // Output = true Matching all values using every() This callback function will loop through an array until one of the conditions evaluates to true: let haystack = Checking for a partial match using some()

So includes() solves the problem of finding out whether a string exists within an array, but what happens if you want to match multiple string values? We could loop, map or filter the values to discover whether they exist, but the array prototype actually has a couple of very useful functions we can utilise. To ‘pass an array’ to includes() we have to try a different approach. The problem with includes() is that it requires a string value and therefore you can’t pass an array to it. Includes() is a simple array function which returns true if the passed value matches a value within the array. Look for a single value in an array using includes() If you want to skip straight to the end there are some ready to go ‘inArray’ style JavaScript functions for you to use. This post will explore how you can find out whether a JavaScript array contains certain values using simple functions to evaluate to true or false. I’ve looked at how to find the closest number in a JavaScript array, but what happens when you simply want to check whether a value (or an array of values) exist within that array? Would you like to be able to pass an array to Includes()?

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Javascript array includes