- Categories: JavaScript Methods, JavaScript Reference, Reference
Quick Reference
The Array filter() method creates a new array filled with elements that pass a test provided by a function, leaving the existing array unchanged.
<!-- html element to place output -->
<p id="my_ages"></p>
// array
let ages = [9, 23, 33, 43];
// function to run
function check_ages(age) {
return age >= 18;
}
// new filtered array
let results = ages.filter(check_ages);
// output all ages equal to or greater than 18 to the HTML element
document.getElementById('my_ages').innerHTML = results;
The way this works (see Syntax section below):
- The filter() method cycles through the array looking for ages greater than or equal to 18 and creates a new array with those items
Output
23,33,43
Syntax
array.filter(function(currentValue, index, arr), thisValue)
Parameters
| Parameter | Description |
|---|---|
| function() | A function to be run for each element in the array (required) |
| currentValue | The value of the current element (required) |
| index | The index of the current element |
| arr | The array of the current element |
| thisValue | A value passed to the function as its "this" value (default is undefined) |
We’d like to acknowledge that we learned a great deal of our coding from W3Schools and TutorialsPoint, borrowing heavily from their teaching process and excellent code examples. We highly recommend both sites to deepen your experience, and further your coding journey. We’re just hitting the basics here at 1SMARTchicken.
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JAVASCRIPT NOTES:
- When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
- JavaScript is a case-sensitive language; firstName is NOT the same as firstname
- Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
- JavaScript variables must begin with a letter, $, or _
- JavaScript variables are case sensitive (x is not the same as X)
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