Question

I do not know whether this has a term for itself or not, but, in PHP I can do:

if ($variable = 5)
{
    echo $variable; // 5
}

Where, the same for JS fails:

if (var variable = 5)
{
    echo variable; // Unexpected token var 
}

Is there an equivalent?

Answer 1

You cannot define a variable inside if block. So, the answer is no, you cannot do this in javascript. In PHP, a variable definition will return true which will drive the if.

But, an assignment statement returns true, so you can use:

var $variable;
if($variable = 5) {
    alert($variable);
}