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
}

Maybe its not an empty string, and instead a string of one or more invisible characters. const id = '­' // or '\u00AD' if stripped by reddit console.log(id) // '' console.log(id.trim().length) // 1

Hi Tabish Kazi, Without looking at the video, I can tell you that in the specific example given, the second code example would lead to the same result as the first code example. The real difference lies in the operator used. In the first example you use the plus-equal operator which reads the current value of the variable and adds the value to the right of the operator to it, then stores the new value to the variable. In the second example, the value to the right of the assignment operator is stored in the variable with no preference to what is already stored in the variable. The thing is though, in order for the plus-equal operator to work, the value of the variable can’t be null or undefined. So say you were looping through a series of properties and you wanted to dynamically create an HTML list item for each valid property without knowing how many list items would need to be created in advance. Well you know you’re going to wrap all this HTML within a string (and later set the innerHtml of some element to be equal to this string). And so you want to continually build upon this HTML string for however long the for loop runs. And so you decide to use the plus-equal operator to add to this string, but if the variable you’re adding to isn’t already a string, then the JS interpreter wouldn’t be able to add the first list item to it (a string of html defined declaratively). The program/code would crash. This is because the interpreter wouldn’t know how to add an undefined value and a string together (just as the interpreter wouldn’t know how to add something like a string and an integer together). So you initialize the variable as an empty string so that the interpreter knows that the variable is indeed a string, and as such, can be concatenated with other strings. I’m thinking that maybe I’ve over explained a bit, but I hope that makes sense. Let me know if it doesn’t.