How to use dynamic string in eval

Question

let value = 'italic';
let varname = "fontSizeTitle";
eval(varname + "=" + value);

console.log(fontSizeTitle)

I have a big project in which i use eval() to assign dynamic variables to dynamic strings. The problem here is it throws an error saying italic is not defined but when if i want to use value as a string but again being dynamic? how do i tell eval() that i want the value to be dynamic. Sorry for not posting my project code but its the exact scenario in here too.

Don't do that. It's an absolute nightmare to maintain and secure. https://stackoverflow.com/questions/5187530/variable-variables-in-javascript — Quentin, Mar 03 '20 at 10:59

score 3 · Accepted Answer · answered Mar 03 '20 at 10:56

Is italic a string literal as opposed to a variable name? If so, you must surround it with quotes in order to set it.

Your current eval statement does this:

fontSizeTitle = italic

This is possibly what it should be:

fontSizeTitle = 'italic'

The following code snippet will show this working:

let value = 'italic';
let varname = "fontSizeTitle";
let statement = varname + "='" + value + "'";
console.log(statement);
eval(statement );

console.log(fontSizeTitle)

I've added the statement itself to the console log so you can see what is actually being executed.

How to use dynamic string in eval

1 Answers1