- Categories: JavaScript Methods, JavaScript Reference, Reference
Quick Reference
The Array map() method creates a new array by calling a function for every array item.
<!-- html element to place output -->
<p id="my_squares"></p>
// array
let numbers = [4, 9, 16, 25, 36, 49];
// output the square roots of all the array items
document.getElementById('my_squares').innerHTML = 'Square Roots: ' + numbers.map(Math.sqrt);
The way this works (see Syntax section below):
- The map() method cycles through the array doing something with each item (in this case, finding the square root)
Output
Square Roots: 2,3,4,5,6,7
Syntax
array.map(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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