Question

I want to test whether a JavaScript variable has a value.

var splitarr =  mystring.split( ' ' ); aparam = splitarr [0] anotherparam = splitarr [1] //.... etc 

However the string might not have enough entries so later I want to test it.

if ( anotherparm /* contains a value */ ) 

How do I do this?

Answer 1

In general it’s sort of a gray area… what do you mean by ‘has a value’? The values null and undefined are legitimate values you can assign to a variable…

The String function split() always returns an array so use the length property of the result to figure out which indices are present. Indices out of range will have the value undefined.

But technically (outside the context of String.split()) you could do this:

js>z = ['a','b','c',undefined,null,1,2,3] a,b,c,,,1,2,3 js>typeof z[3] undefined js>z[3] === undefined true js>z[3] === null false js>typeof z[4] object js>z[4] === undefined false js>z[4] === null true