I want to check if the window.sessionStorage object exists. Is this the way to do it:
if (window.sessionStorage)
in javascript?
3 Answers
if(sessionStorage.length == 0) {
//do something
}
That will validate whether sessionStorage is empty or not. Alternatively, you can use this:
if(typeof(sessionStorage) == 'undefined') {
//do something
}
1 Comment
Peter
The first check here could possibly fail, since if
sessionStorage didn't exist on the global object, there would be an exception.Your proposed solution will work since we know that the sessionStorage property must refer to an object—and objects always resolve truthy in expressions.
However a word of caution, when checking for the existence of any arbitrary property in JavaScript (where we don't necessarily know the value), it's safest to check that the key exists in the object of interest. For example:
var exists = (someObject && 'someProp' in someObject);
We need to do this because someProp could be a valid property yet the test would fail when equal to: false, "", 0, or any other value that would be falsey in an expression.
sessionStorage(which is not common; you should probably check for specific keys instead), use what you have in the question and not what was written in the answers.