Browser compatibility analysis of setTimeout and setInterval_Basic knowledge

When I accidentally tested the browser compatibility of AJAXRequest, I found that the AJAXRequest.update method had problems in IE in some cases. After testing, I found that the problem was setTimeout and setInterval.
The problem occurs when calling the AJAXRequest.update method. If the update interval and the number of updates are provided, then problems will occur under IE. The specific manifestation is that when the update interval is provided, the function works, and when the update number is provided, the function Unable to stop execution after the specified number of updates.
After testing several examples, I found the problem. In IE, setTimeout and setInterval do not support parameter passing.
Demo address: http://www.xujiwei.cn/demo/usetimer/
The syntax of setTimeout found in Netscape’s JavaScript reference is as follows:

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setTimeout
Evaluates an expression or calls a function once after a specified number of milliseconds elapses.
Syntax
setTimeout(expression, msec)
setTimeout(function, msec, arg1, ..., argN)
Parameters
expression A string containing a JavaScript expression.
msec A numeric value or numeric string, in millisecond units.
function Any function.
arg1, ..., argN (Optional) The arguments, if any, passed to function.

The second way to use it is to define A timer, when executing the function, will pass the parameters defined when calling setTimeout to the function. However, in IE, this method of calling is not supported, that is, when the function is executed, the function does not receive these parameters. parameter. For example:

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In Firefox and Opera, the browser can correctly pop up the prompt box to display the string "my site: www.xujiwei.cn", while in IE, What is displayed is "my site: undefined", which means that the function show did not receive the parameter str, so it is displayed as an undefined variable.
Of course, if the variables used inside the function are global variables, there is no need to consider these issues, such as:

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This code works normally in IE and Firefox, displaying "my site: www.xujiwei.cn".
When the variable is a global variable, you can use a statement segment to call setTimeout, that is, use the first syntax:

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Because the variable url is a global variable, the statement segment "show(url);" defined by the timer execution can correctly pass parameters, but if url is not a global variable, When it is a local variable, the execution result will be wrong:

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An error will occur at this time. When the function test is executed, it will prompt that the url is undefined. When executing the defined statement segment "show (url);", the context has been separated from the function test, and the url is defined inside the function test, so when the function test is executed, the variable url has been released.
If you want to use local variables in setTimeout and solve the problem that setTimeout in IE does not support parameter passing, you can use an anonymous function, that is, define an anonymous function when calling setTimeout, and perform the original needs inside this function. operate.

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In the above example, an anonymous function is defined when calling setTimeout, and its function body is "show(url);". Because the function has been defined, when the timer calls this function , the variable url is still referenced, because some functions can be executed correctly, and the string "my site: www.xujiwei.cn" is displayed.
In general, you need to pay attention to the following points when using setTimeout or setInterval:
1. If you use an expression when defining a timer, the variable in it should be a global variable or a direct value , and cannot be a local variable.
2. When defining a timer, if you define a calling function, you should only write the function name without adding parentheses. If you add it, you will define the return value.
3. Parameters cannot be passed when using timers in IE.
4. If you want to pass parameters when using a timer in IE, you can use an anonymous function and call the originally called function in the function body.

Please correct me if there are any errors.