How to declare variable names dynamically in java script? [duplicate]

I have an array:

var arr = ['a', 'b', 'c'];

I need to declare within a for loop, variables value_x- when x is each one of the array value.

what I've tried:

var i;
for(i=0;i<3;i++){
    var x = 'hello there';
    var str = 'var ' + `value_${arr[i]}` + ' = ' + "'" + x + "'" + ';'
    eval(str);
}

now, str =

var value_a = 'hello there';

but the eval() call return this error:

error: EvalError: Dynamic code evaluation disallowed‏

now, I saw also solution which used window object, like:

window[`value_${arr[i]}`] = x;

and this also return error:

error: ReferenceError: window is not defined

which because this is local script, not on the server. please help.‏ ‏

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