javascript check if string is null or empty or undefined code example

Example 1: javascript syntax for check null or undefined or empty

if (typeof value !== 'undefined' && value) {
    //deal with value'
};

Example 2: javascript if string empty

// Test whether strValue is empty or is None
if (strValue) {
    //do something
}
// Test wheter strValue is empty, but not None 
if (strValue === "") {
    //do something
}