The alert () function in JavaScript use the technique to explain _javascript techniques

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

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

This can be simplified as a direct use of the alert () function:

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Simplified alert () usage
Alert ("Sample text");

If you need to display text with a newline, you can use \ n:

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Use \ n in alert ()
Alert ("The line\nthe second line");

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

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Use \ t in alert ()
Alert ("Alex\t50\t34\nbob\t59\t38");

Use of variables

In addition to displaying a static string, the alert () function can accept a variable and concatenate the value of the variable with another string:

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

Unfortunately, although the alert () function can accept a variable, it only ends with this string concatenation operation; the alert () function does not accept the practice of passing arguments to a string, as opposed to another debugging method, Console.log (). Take the following code as an example:

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

If the alert () function takes a string pass, the expected output will be "Bob is years old." But the alert () function does not support this, so the final output is '%s is '%d years old. '

pop-up window style

Because the pop-up box used by the alert () function is a browser system object rather than a Web page document object, the style-html label for the pop-up box cannot be defined by using an HTML tag in the alert () function to be displayed intact. For the following code:

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Try to use HTML tags in alert (), would fail
Alert ("<b>test text</b>");

The output is not bold "Test Text."

If you do need to change the style of the alert box, there are two options:

1. Use Unicode characters in the alert () function. The benefits of this approach are simple to implement, but their limitations are obvious: Unicode characters are very limited in their expressiveness.

2. Instead of using the alert () function, use the HTML component to simulate a pop-up box (for example, using the jquery UI Dialog). The advantage of this scheme is that the performance of the pop-up box is strong, but its use will increase the complexity of the front-end code.

Conclusion

The alert () function can be used to alert a user to information or to debug a program. For the former, using components such as the jquery UI dialog can dramatically increase the expressiveness and user experience, and for the latter, because the alert () pop-up blocks the execution of JavaScript code, in many cases using Console.log () To debug a program is a better solution.