How to use array map in JavaScript
In this article, I am going to explain array map() in JavaScript.
Array map method in JavaScript
The JavaScript array map method creates a new array with the result of provided function on every element in this array.
Syntax of array map method
array.map(callback[, thisArgs);
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Parameters in array map method:
-
arrary
Array required an array object.
-
callback
Callback function accepts up to three arguments, and callback function is produce an element of the new array from the array of current one.
-
thisArgs
ThisArgs is used as this when executing callbacks.
Return value in map method
A new array in which each element is the callback function return value for the associated original element.
Exception in map method
If callback argument is not a function object, A TypeError exception is fire.
There are the following callback function parameter:
Parameter |
Value |
value |
Array element value. |
index |
Numeric index of the array element. |
Example of array map method:
<!DOCTYPE html>
<html>
<head>
<title>JavaScript Array map()</title>
</head>
<body>
<script type="text/javascript">
if (!Array.prototype.map) {
Array.prototype.map = function (fun /*, thisp*/) {
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var res = new Array(len);
var thisp = arguments[1];
for (var i = 0; i < len; i++) {
if (i in this)
res[i] = fun.call(thisp, this[i], i, this);
}
return res;
}; }
var numbers = [1, 2, 5];
var roots = numbers.map(Math.sqrt);
document.write("roots is : " + roots);
</script>
</body>
</html>
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OutPut:
roots is : 1,1.4142135623730951,2.23606797749979
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