Question

How to avoid using undeclared variables in JavaScript

Answer 1

"use strict"; // global scope - you can not use undeclared variable (z in this program)
var x = 12
var y = 2

try 
{
    z = x / y;
    document.write(z);
}
catch(err) 
{
    document.write(err);
}


/*
run:

ReferenceError: assignment to undeclared variable z  

*/

 

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Answer 2

"use strict";      

try 
{
    document.write(x);
}
catch(err) 
{
    document.write(err);
}


/*
run:

ReferenceError: x is not defined   

*/

 

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