Functions of JavaScripteval ()

When I was a beginner at JS, I knew this function, but I never understood its purpose, and I kept my eyes closed.

When I was a beginner at JS, I knew about this function, but I never knew about its purpose. I always kept one eye closed and one eye closed. This time I will take a deeper look at the role of this function.

The function of eval is actually very simple. It is to pass a string to the JS interpreter. The Javascript interpreter interprets the string as Javascript code and runs it. The syntax is eval (string), and string is required. The string to be calculated, which contains the JavaScript expression to be calculated or the statement to be executed. Returns the string value (if any ).

This method only accepts the original string as the parameter. If the string parameter is not the original string, this method will be returned without any change. Therefore, do not pass a String object as a parameter for the eval () function.

If you try to override the eval attribute or assign the eval () method to another attribute and call it through this attribute, ECMAScript can throw an EvalError exception.

If the parameter does not contain valid expressions and statements, a SyntaxError exception is thrown. If eval () is illegally called, an EvalError error is thrown. If the Javascript code passed to eval () generates an exception, eval () will pass the exception to the caller.

The simplest example is as follows: