Detailed explanation of tips for using alert() function in JavaScript

In JavaScript code, you can use the alert() function of the window object to display a piece of text to debug the program or alert the user to relevant information:

//Use window object's alert() function
window.alert("sample text");

This writing method can be simplified to using the alert() function directly:

//Simplified alert() usage
alert("sample text");

If you need to display text with line breaks, you can use n:

//Use \n in alert()
alert("The first line\nThe second line");

If you need to use tab characters, you can use t:

//Use \t in alert()
alert("Alex\t50\t34\nBob\t59\t38");

Usage of variables

In addition to displaying static strings, the alert() function You can also accept variables and concatenate the variable values ​​​​with other strings:

//Use variable in alert()
var word = "life";
alert("The magic word is: " + word + ". Don't panic.");

Unfortunately, although the alert() function can accept variables, it can only do this string concatenation operation; with another In contrast to the debugging method console.log(), the alert() function does not accept passing parameters to a string. Take the following code as an example:

//Try to use parameter in alert(), will fail
var name = "Bob";
var years = 42;
alert("%s is %d years old.", name, years);

If the alert() function accepts a string parameter, the expected output result will be "Bob is 42 years old."; but in fact the alert() function does not support this. Therefore, the final output result is "%s is %d years old."

Pop-up window style

Since the pop-up box used by the alert() function is a browser system object rather than a web page document object, the pop-up box cannot be defined by using HTML tags in the alert() function style - HTML tags will be displayed intact. For the following code:

//Try to use HTML tags in alert(), will fail
alert("<b>Test Text</b>");

The output result is not the bold "Test Text".

If you really need to change the style of the alert box, you have the following two options:

1. Use Unicode characters in the alert() function. The advantage of this solution is that it is very simple to implement, but its limitations are also obvious: the expressive power of Unicode characters is very limited.

2. Instead of using the alert() function, use HTML components to simulate pop-up boxes (such as using jQuery UI Dialog). The advantage of this solution is that the pop-up box will be very expressive, but its use will increase the complexity of the front-end code.

Conclusion

alert() function can be used to warn users of information and can also be used to debug programs. For the former, using components such as jQuery UI Dialog can greatly increase expressiveness and user experience; for the latter, since the alert() pop-up box will block the execution of JavaScript code, in many cases, console.log() is used to Debugging the program is a better solution.

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