Use Jquery's val() method_jquery

Look at the following example:

Copy code The code is as follows:

Code:

Copy code The code is as follows:

$("#address").focus(function() { // The address box gets the mouse focus
var txt_value = $(this).val(); // Get the value of the current text box
if(txt_value==this.defaultValue){
$(this ).val(""); // If the conditions are met, clear the text box content
}
});

Note: this.defaultValue is the default value of the current text box .
The val() method has another use, that is, it can enable the corresponding items of select (drop-down list box), checkbox (multi-select box) and radio (radio button) to be selected, which is often used in form operations. Will be used. Look at the following example:

Copy the code The code is as follows:

< ;input type="button" value="Set radio button and multi-select box selection"/>



Select No. 1
Select No. 2
Select number 3
Select number 4
Select 5 No.


Select No. 1
Select No. 2
Select No. 3
Select No. 4
Select No. 5





Multiple choice 1
Multiple choice 2
Multiple choice 3
Multiple choice 4


Single choice 1
Single choice 2
Single choice 3

After running, the default display effect is as follows:

What should I do if I want to change the selected item at this time? Add the following code in the javascript area:

Copy the code The code is as follows:

$(function() {
//Set the radio drop-down box to select
$("input:eq(0)").click(function(){
//$("#single").val("Select No. 5");
$("#single").val("5"); // and $("#single").val("Select No. 5"); can achieve the effect
var options=$('#single option:selected')
alert(options.val());
});
//Set the multi-select drop-down box to select
$( "input:eq(1)").click(function(){
// $("#multiple").val(["Select No. 2", "Select No. 3"]);
$ ("#multiple").val(["3", "4"]); //Assign value in the form of array
});
//Set radio button and multi-select box selection
$("input:eq(2)").click(function(){
$(":checkbox").val(["check2","check3"]); //Assign value in the form of array
$(":radio").val(["radio2"]);
});
});

Then click the following three buttons:

You will find that the default selected item has changed to the item you want to set. As shown below:

The above is a wonderful use of jquery's val() method. I hope it will be helpful when you operate multi-select and check boxes.