In jquery, the map() function returns a new encapsulated array using the specified function; this function is used to use the specified function to process each element in the array or each attribute of the object, and The processing result is encapsulated and returned as a new array; the return value of this function will be used as an element in the result array. If the return value is null or undefined, it will not be added to the result array.
The operating environment of this tutorial: windows10 system, jquery3.6.0 version, Dell G3 computer.
map in jquery
jQuery.map() function is used to process each element in the array (or each attribute of the object) using the specified function, and encapsulate the processing result as a new Array returned.
Note:
1. Before jQuery 1.6, this function only supported traversing arrays; starting from 1.6, this function also supports traversing objects.
2. map() will also pass in two parameters to the function: one is the element or attribute value of the current iteration, and the other is the array index or object attribute name of the current iteration item.
3. The return value of this function will be used as an element in the result array. If the return value is null or undefined, it will not be added to the result array.
Syntax
$.map( object, callback )
object Array/Object type specifies the array or object that needs to be processed.
callback Function type specifies the processing function.
Examples are as follows:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>123</title>
<style>
div { color:blue; }
p { color:green; margin:0; }
span { color:red; }
</style>
<script src="js/jquery.min.js"></script>
</head>
<body>
<div></div>
<p></p>
<span></span>
<script>
$(function () {
var arr = [ "a", "b", "c", "d", "e" ];
$("div").text(arr.join(", "));
arr = $.map(arr, function(n, i){
return (n.toUpperCase() + i);
});
$("p").text(arr.join(", "));
arr = $.map(arr, function (a) {
return a + a;
});
$("span").text(arr.join(", "));
})
</script>
</body>
</html>Examples are as follows:
##Expand knowledge:
There is a map method in our native js, and there is also a map method in jQuery. What is the difference between them? As usual, look at the code first
The first parameter: the currently traversed element
However, note: Like the forEach method of native js, pseudo arrays cannot be traversed
There is no doubt that an error is reported, which proves that the map method of native js cannot traverse pseudo arrays
## The first parameter: the array to be traversed
Second parameter: The callback function executed after each element traversed
Parameters of the callback function:
First parameter: The traversed element
Second Parameters: The traversed index
can traverse the array just like the native js map method
So can it traverse the pseudo array? So let’s get straight to the code!
Since both the each and map methods in jQuery can traverse arrays and pseudo-arrays, what is the difference between them?
- The default return value of each method is to return whoever is traversed
- 2. The default return value of the map method is an empty array
1. The each method does not support processing the traversed array in the callback function
2. The map method can be used in the callback function Process the traversed array through return, and then generate a new array to return 
And each does not support processing the traversed array in the callback function through return
The above comparison should be Now that you understand the difference between them, you should have a clear understanding of when to use the map method and when to use the each method, right?
Video tutorial recommendation: jQuery video tutorial
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