Introduction to the method $.inArray() for traversing arrays in jQuery.

The $.inArray() method is a jQuery function that is used to find the index position of a specified value in an array.

Syntax: $.inArray(value, array)

Parameter:

1. value: the value to be searched for
2. array: the array to be searched

Return value:
If the specified value is found, return its index in the array; otherwise, return -1.

Example:

var arr = [1, 2, 3, 4, 5];
var index = $.inArray(3, arr);
console.log(index); // 输出: 2

var index2 = $.inArray(7, arr);
console.log(index2); // 输出: -1

In this example, we first create an array named arr, then use the $.inArray() method to find the index position of the element with a value of 3 in the array, which is 2. Next, we try to find the element with a value of 7, but since this element does not exist in the array, it returns -1.

It’s important to note that the $.inArray() method only returns the index position of the first matching value found in the array. If there are multiple identical values in the array, it will only return the index of the first match. To find all matching index positions, you can use the $.map() method instead.