JavaScript syntax
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str += "e"; // "abcde"
const str2 = "2" + 2; // "22", not "4" or 4.
??
JavaScript's nearest operator is ??, the "nullish coalescing operator", which was added to the standard in ECMAScript's 11th edition.cite-ref-18[18] In earlier versions, it could be used via a Babel plugin, and in TypeScript. It evaluates its left-hand operand and, if the result value is not "nullish" (null or undefined), takes that value as its result; otherwise, it evaluates the right-hand operand and takes the resulting value as its result.
In the following example, a will be assigned the value of b if the value of b is not null or undefined, otherwise it will be assigned 3.
const a = b ?? 3;
Before the nullish coalescing operator, programmers would use the logical OR operator (||). But where ?? looks specifically for null or undefined, the || operator looks for any falsy value: null, undefined, "", 0, NaN, and of course, false.
In the following example, a will be assigned the value of b if the value of b is truthy, otherwise it will be assigned 3.
const a = b || 3;
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