if isset javascript equivalent

I'm looking for a solution for the javascript version of if isset in php. This is what I have:

if (typeof obj.office !='') 
  	{( document.listingform.office.value.length < 3 ); 
		{ if (valid)
    document.listingform.office.style.border="solid 1px red";
    msg+="\"Office\" field cannot contain less than three characters\n";
    valid = false;

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What I want to to do is if the field "office" holds a value and is less than three characters then alert but only if it has a value. How can I do that.
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>> if (typeof obj.office !='')
One possible implementation of"isset" equivalent check would be:

// NOTE: My implementation below checks a single value at a time.  By contrast,
// the php version accepts multiple arguments and returns TRUE only if all of the
// arguments are set.  If you want an implementation that checks multiple 
// arguments then refer to the link at the end of the post.
function isset(val){
return (typeof(val)!=='undefined' && val!==null);

if( isset(obj.office) )

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In case you are interested, here's another.  That site has various PHP functions implemented in js
Alexandre SimõesManager / Technology SpecialistCommented:
This is the shortest option:
if (obj.office && obj.office.length < 3) {
    // your code

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