1if( typeof myVar === 'undefined' || myVar === null ){
2 // myVar is undefined or null
3}
1if(typeof comment === 'undefined') {
2
3 alert('Variable "comment" is undefined.');
4
5} else if(comment === null){
6
7 alert('Variable "comment" is null.');
8
9}
1var myVar=null;
2
3if(myVar === null){
4 //I am null;
5}
6
7if (typeof myVar === 'undefined'){
8 //myVar is undefined
9}
10
1var myVar=null;
2
3if(myVar === null){
4 //I am null;
5}
6
7if (typeof myVar === 'undefined'){
8 //myVar is undefined
9}