What is the best way to test for an empty string with jquery-out-of-the-box, i.e. without plugins? I tried this.
But it did't work at least out-of-the-box. It would be nice to use something that's builtin.
I wouldn't like to repeat
if (a == null || a=='')
everywhere if some if (isempty(a))
would be available.
This question is related to
javascript
jquery
Try this
if(!a || a.length === 0)
Try executing this in your browser console or in a node.js repl.
var string = ' ';
string ? true : false;
//-> true
string = '';
string ? true : false;
//-> false
Therefore, a simple branching construct will suffice for the test.
if(string) {
// string is not empty
}
Check if data is a empty string (and ignore any white space) with jQuery:
function isBlank( data ) {
return ( $.trim(data).length == 0 );
}
Based on David's answer I personally like to check the given object first if it is a string at all. Otherwise calling .trim()
on a not existing object would throw an exception:
function isEmpty(value) {
return typeof value == 'string' && !value.trim() || typeof value == 'undefined' || value === null;
}
Usage:
isEmpty(undefined); // true
isEmpty(null); // true
isEmpty(''); // true
isEmpty('foo'); // false
isEmpty(1); // false
isEmpty(0); // false
The link you gave seems to be attempting something different to the test you are trying to avoid repeating.
if (a == null || a=='')
tests if the string is an empty string or null. The article you linked to tests if the string consists entirely of whitespace (or is empty).
The test you described can be replaced by:
if (!a)
Because in javascript, an empty string, and null, both evaluate to false in a boolean context.
To checks for all 'empties' like null, undefined, '', ' ', {}, [].
var isEmpty = function(data) {
if(typeof(data) === 'object'){
if(JSON.stringify(data) === '{}' || JSON.stringify(data) === '[]'){
return true;
}else if(!data){
return true;
}
return false;
}else if(typeof(data) === 'string'){
if(!data.trim()){
return true;
}
return false;
}else if(typeof(data) === 'undefined'){
return true;
}else{
return false;
}
}
Use cases and results.
console.log(isEmpty()); // true
console.log(isEmpty(null)); // true
console.log(isEmpty('')); // true
console.log(isEmpty(' ')); // true
console.log(isEmpty(undefined)); // true
console.log(isEmpty({})); // true
console.log(isEmpty([])); // true
console.log(isEmpty(0)); // false
console.log(isEmpty('Hey')); // false
if((a.trim()=="")||(a=="")||(a==null))
{
//empty condition
}
else
{
//working condition
}
if(!my_string){
// stuff
}
and
if(my_string !== "")
if you want to accept null but reject empty
EDIT: woops, forgot your condition is if it IS empty
Since you can also input numbers as well as fixed type strings, the answer should actually be:
function isBlank(value) {
return $.trim(value);
}
Source: Stackoverflow.com