how to check iof a variable has a vale with an if statement in js code example

Example 1: javascript check if variable exists

if (typeof myVar !== 'undefined') {
    // myVar is defined
}

Example 2: How can I test whether a variable has a value in JavaScript?

if (typeof variable == "undefined") {...} --> return true if variable undefined

//An empty string evaluates to FALSE in JavaScript so you can just do:
if (variable) {...}