The three dialog boxes of JavaScript are called by the three methods of the Window object alert (), confirm (), and prompt ()

First type: Alert () method

The alert () method is the easiest to use in these three dialog boxes, and she can be used to simply and clearly display the text information in the alert () parentheses in the dialog box, which we call the Alert dialog box, where the information to display is enclosed in parentheses, and the dialog box contains a "Confirm" button. Once the user has finished reading the displayed information, you can close the dialog box by simply clicking the button. Here's an example of using the alert () method, as shown in the following code:

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<title>编写html页面</title><script language="javascript"> //JavaScript脚本标注alert("上联：山石岩下古木枯");//在页面上弹出上联alert("下联：白水泉边少女妙");//在页面上弹出下联</script>

Perform the small example above, pop up the dialog box on the page and display a sentence "Top of the line: the ancient wood withered under the Rocks Rock", as follows:

Next, click on the "Confirm" button to display the second dialog box and display "White water spring side girl wonderful!" ", the effect is as follows;

Pop up the dialog on the page and display a sentence "top line: Ancient wood withered under Rocks Rock", click the "Confirm" button and then display the 2nd dialog box and display "White water spring side of the girl wonderful!" "Let's analyze This little example:

A, call the alert () method two times in the <script> script block;

b, in each alert () in parentheses to add a piece of text information, run appears as shown in the page, when using the mouse click on the page "OK" button, the second page appears, and then click the "OK" button to close the dialog box on the page. Note: The two dialogs are displayed separately instead of one overwriting the other, because JS actually executes the first alert () and waits until the user clicks the "Confirm" button to execute the second alert ().

Alert () is a method of the Js window object, which can be written as window.alert () or as alert (), which produces a dialog box with a confirmation button that shows the information in parentheses.

Second type: Confirm () method

The Confirm () method is very similar to the use of the alert () method, except that there is a "cancel" button in addition to a "Confirm" button in the dialog box called the confirmation dialog box, which calls the confirm () of the Window object. Method and the prompt () method described later can also not write window. Here's a small example of confirm (), as shown in the code below:

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<title>编写html页面</title><script language="javascript"> //js脚本标注confirm("上联：一但重泥拦子路；下联：两岸夫子笑颜回"); //在页面上弹出确认对话框</script>

The display results are as follows:

Analyze This small example:

A, add the Confirm () method to the <script> script block,

b, a text message is added within confirm (), the effect is as shown, if the user clicks the Confirm button, the Confirm () method returns True, and if the user clicks the Cancel button, the Confirm () method returns false regardless of which button the user chooses , the dialog box is closed, and the JavaScript code continues to be executed. Click the "Confirm" or "Cancel" button is to close the dialog box, there seems to be no difference, in fact, whether you click the "Confirm" or "Cancel" button will return a Boolean value, so that there are some JS code behind the scenes to play the role of the button, please look at the following example, experience using confirm () Returns the beauty of a Boolean value. The code is as follows:

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<title>编写html页面</title><script language="javascript"> //js脚本标注var con;con=confirm("你喜欢玫瑰花么?"); //在页面上弹出对话框if(con==true)alert("非常喜欢!");else alert("不喜欢!");</script>

Let's examine this small example:

A, a variable con is declared in the <script> script block.

B, con=confirm () A sentence assigns the Boolean value returned by the Confirm () method to con.

C, the use of the value of con by the IF statement, the execution of different statements, the effect is as follows:

If you click the OK button on the confirmation box on the page, the page appears as shown:

If you click the Cancel button, the page appears as shown:

The third type: Prompt () method

The alert () method is very similar to the Confirm () method in that it displays only the information that is already present, but the user cannot enter his or her own information, but prompt () can do this, not only to display the information, but also to provide a text box that asks the user to enter their own information using the keyboard, She also contains "confirm" or "Cancel" two buttons, if the user "Confirm" button, then the prompt () method returns the content that the user entered in the text box (is the string type) or the initial value (if the user did not enter the information); If the user clicks the Cancel button, prompt () The method returns NULL, which we call the dialog box, where she has the best interactivity in the three dialog boxes.

Look at a small example: on the page two pop-up prompt dialog box, so that users can enter information, the code is as follows:

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<title>编写html页面</title><script language="javascript"> //js脚本标注var name,age;name=prompt("请问你叫什么名字?"); /*在页面上弹出提示对话框，将用户输入的结果赋给变量name*/alert(name); //输出用户输入的信息age=prompt("你今年多大了?","请在这里输入年龄"); /*在页面上再一次弹出提示对话框，讲用户输入的信息赋给变量age*/alert(age)//输出用户输入的信息</script>

To run the above program, the effect is as follows:

Click OK, there will be so surprise nie:

We then click the OK button:

Then click the OK button:

Analyze This little example

A, two prompt () methods have been added to the <script> script block.

B. A text message is added to the first prompt () parenthesis.

C, Name=prompt () is to assign the information that the user entered in the text box to the variable name.

Differences and connections between alert (), confirm (), prompt ():

Alert Box alert ()

Alert is a warning box, and only one button "OK" has no return value, and the warning box is often used to ensure that the user can get some information. When the warning box appears, the user needs to click the OK button to continue the operation. Syntax: alert ("text").

Confirmation Box confirm ()

Confirm is a confirmation box, two buttons, OK or Cancel, return True or false. The confirmation box is used to enable users to verify or accept certain information. When the confirmation box appears, the user needs to click the OK or Cancel button to continue the operation. If the user clicks Confirm, then the return value is true. If the user clicks Cancel, the return value is false. Syntax: Confirm ("text")

Cue box prompt ()

Prompt is a prompt box that returns the input message, or its default value hint box is often used to prompt the user to enter a value before entering the page. When the prompt box appears, the user needs to enter a value and then click the Confirm or Cancel button to continue the manipulation. If the user clicks Confirm, then the return value is the value entered. If the user clicks Cancel, the return value is null. Syntax: Prompt ("text", "Default value")

The three dialog boxes of JavaScript are called by the three methods of the Window object alert (), confirm (), and prompt ()