How to determine if the checkbox is all selected in jquery

Judgment steps: 1. Get all checkbox elements, the syntax "$("input[type='checkbox']")" will return a jQuery object; 2. Select all selected elements, the syntax "$ (":checked")" will return a JQ object; 3. Calculate the length of the two objects and determine whether the two lengths are equal. The syntax is "checkbox element object.length==selected element object.length". If they are equal, then Select all, otherwise, not all are selected.

The operating environment of this tutorial: windows7 system, jquery3.6.1 version, Dell G3 computer.

Jquery method to determine whether the checkbox is all selected: Check whether the number of multi-selected elements in the checkbox is equal to the number of selected elements.

Implementation steps:

Step 1: Use the attribute value selector to obtain the checkbox element

$("input[type='checkbox']")

will be returned A jQuery object containing all checkbox elements.

Step 2: Use the :checked selector to select all selected elements

$(":checked")

will return a jQuery object containing all selected elements.

Step 3: Use the length attribute to calculate the length of the two jQuery objects and determine whether the two lengths are equal

checkbox元素对象.length==选中元素对象.length

• If equal (return If the value is true), then the checkbox is all selected

• If they are not equal (the return value is false), then the checkbox is not all selected

Implementation example: Determine whether the checkbox is all selected

	
		
		
		
	
	
		
 
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##Extended knowledge: attribute value selector

$("[attribute|='value']")<strong></strong>

Select the specified attribute value equal to the given string or change the string to a prefix ( The string is followed by a hyphen ("-").

attribute: an attribute name

value: an attribute value

$(function(){

    $('a[hreflang|="en"]').css("border","2px solid red");
        //查找hreflang属性值是英语的所有链接。
});

$("[attribute*='value']")<strong></strong>

Selects elements with a specified attribute that contains a given substring. (The given attribute is selected to contain elements with certain values)

attribute: an attribute name
value: an attribute value, which can be a word without quotes, or a quoted string.

$(function(){
    $('input[name*="man"]').css("border","2px solid red");
        //查找所有 input 的 name 属性中带有 'man' 的元素，并添加边框
});

$("[attribute~='value']")<strong></strong>

Select the space-separated value of the specified attribute to include one the given element.

attribute: an attribute name
value: an attribute value, which can be a word without quotes, or a quoted string.

$(function(){

    $('input[name~="man"]').css("border","2px solid red");
        //查找所有属性中含有 'man' 这个单词的文本框，并且修改其文本值。
})

$("[attribute$='value']")

Select the element whose specified attribute ends with the given element. This element comparison is case-sensitive.

attribute: an attribute name
value: an attribute value, which can be a word without quotes, or a quoted string.

$(function(){
    $('input[name$="letter"]').css("border","2px solid red");
            //查找所有的属性名称以"letter"的结束，并把他们的文字输入。
})

$("[attribute='value']") Selects elements whose specified attribute is the given value.
attribute: an attribute name.
value: An attribute value, which can be a word without quotes, or a quoted string.

$(function(){
    $('input[value="Hot Fuzz"]').next().text("Hot Fuzz");
        //查找input 中 value 值等于 Hot Fuzz 的将其后面的元素添加文本。
})

$("[attribute!='value']") Select the element whose specified attribute is not equal to this value
attribute: one Attribute name
value: An attribute value, which can be a word without quotation marks, or a quoted string.

$(function(){
    $('input[name!="newsletter"]').next().append("<b>；not newsletter</b>")
            //查找input 中name 不等于 newletter 的下一个元素追加 文本。
                注：主要含有这个字符串就行。
})

$("[attribute^='value']") Select the element that starts with the given string with the specified attribute.
attribute: an attribute name
value: an attribute value, which can be a word without quotation marks, or a quoted string.

$(function(){
    $('input[name^="news"]').val("news here!");
    //查找input 中 name 中含有new 这个字符串的 添加value 值。
})

$("[attribute]") Selects all elements with the specified attribute, which can be any value.
attribute: an attribute name.

$(function(){
    $('div[id]').css("color","red")
            //给绑定id属性的div的文本颜色变成红色。
})

$("[attributeFilter1][attributeFilter2]attributeFilter3")## Select elements that match all specified attribute filters

attributeFilter1: An attribute filter

attributeFilter2: Another attribute filter, used to further reduce the selected elements.
attributeFilterN: There are more attribute filters as needed.

$(function(){
    $('input[id][name$="man"]').val('only this one')
    //查找那些有id属性，并且name 属性以man结尾的输入框，并设置值。
})

【Recommended learning: jQuery video tutorial

, web front-end video】

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