A brief discussion on the function and scope of eval()

The role of eval()

Parses string parameters into js code and runs it, and returns the execution result;

The scope of eval

The scope is valid in all its scope contents

IE8 and below point to window

Solution:

1. functiona(){

2. if(window.execScript){ // Supports IE8 and below versions

3. window.execScript("var x=1");

4. }

5. else{ //Commonly used browsers support

6. ## window.eval(

   "var x=1 ");

7. }

8. console.log(x);

9. }

10. a();

11. console.log(x);

Notes

You should avoid using eval, which is unsafe and very performance-consuming (twice, once parsed into a js statement and once executed).

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