check variable undefined javascript code example
Example 1: js if not undefined
if (typeof myVar !== "undefined") {
console.log("myVar is DEFINED");
}
Example 2: javascript check for undefined
if (typeof myVariable === 'undefined'){
}
Example 3: javascript if undefined
if(typeof comment === 'undefined') {
alert('Variable "comment" is undefined.');
} else if(comment === null){
alert('Variable "comment" is null.');
}
Example 4: test if is undefined javascript
let id;
if(typeof id === 'undefined') {
console.log("id is undefined...");
}
Example 5: nodejs check if variable is undefined
if ( typeof query !== 'undefined' && query )
{
}
else
{
}
Example 6: javascript check undefined
if(myVar === null) {
console.log("Element is undefined");
}