How to use eval in javascript
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The eval function in javascript is used to evaluate a string and executes the JavaScript code in it. The syntax for this function is "eval (string)", and the parameter string represents the string to be evaluated.
This article operating environment: windows7 system, javascript1.8.5 version, DELL G3 computer.
The usage of eval in javascript
The eval () function evaluates a string and executes the JavaScript code in it.
Grammar
Eval (string)
The parameter string must be the string to evaluate that contains the JavaScript expression to evaluate or the statement to execute.
Return value: the value obtained by calculating the string, if any.
Description
This method only accepts the original string as a parameter, and if the string parameter is not the original string, then the method will return without any change. So do not pass a String object as an argument to the eval () function.
If you try to override the eval property or assign the eval () method to another property and call it through that property, the ECMAScript implementation allows an EvalError exception to be thrown.
Throw out
If there is no legal expression and statement in the parameter, a SyntaxError exception is thrown.
If eval () is called illegally, an EvalError exception is thrown.
If the Javascript code passed to eval () generates an exception, eval () passes the exception to the caller.
Tip: although eval () is very powerful, it is rarely used in practice.
Example
In this example, we will apply eval () on several strings and look at the result returned:
Eval ("Xerox 10 / 20; [xss_clean] (Xeroy)") [xss_clean] (eval ("2x / 2")) var x = 10 [XSS _ clean] (eval (x / 17)
Output:
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