javascriptnullis-empty

How do I check for an empty/undefined/null string in JavaScript?


Is there a string.Empty in JavaScript, or is it just a case of checking for ""?


Solution

  • Empty string, undefined, null, ...

    To check for a truthy value:

    if (strValue) {
        // strValue was non-empty string, true, 42, Infinity, [], ...
    }
    

    To check for a falsy value:

    if (!strValue) {
        // strValue was empty string, false, 0, null, undefined, ...
    }
    

    Empty string (only!)

    To check for exactly an empty string, compare for strict equality against "" using the === operator:

    if (strValue === "") {
        // strValue was empty string
    }
    

    To check for not an empty string strictly, use the !== operator:

    if (strValue !== "") {
        // strValue was not an empty string
    }