check empty text

Question

i have statement like this

var a = $("#txt1").val().trim()

how should check if 'a' is not empty

Answer 1

if (a !== null) {
    /* Do stuff */
}

Answer 2

this should do

if(a != '') {
  // alert(a);
}

Answer 3

I think

if (a) { /* a is not empty */ }

should do the trick, perhaps unless a contains "false" (not sure of that) but I suppose you could do

if (a !== null && a.length != 0) { /* a is not empty */ }

Answer 4

if ( a !== "" ) { }