What is the most efficient method to convert this JavaScript code into Typescript?
let a, b; /* @type {string | null} */
a += b;
One possible solution is
let a: string | null, b: string | null;
a = a || '' + b || '';
However, this approach sacrifices some of the simplicity of the original code. Are there any other alternative ways to achieve the same result?
While it may not be crucial in this situation, you might want to consider utilizing the nullish coalescing operator (??) instead of ||. This operator only returns the value on the right if the value on the left is specifically null or undefined, rather than any falsy value like ''.
You can approach this in two different ways:
// Using your original method
// Keep in mind that + has higher precedence than ?? and ||, so parentheses are necessary here
a = (a ?? '') + (b ?? '')
// Set a default value for a first
a ??= ''
// Then add b or '' if b is null to a
a += b ?? ''
The ??= syntax belongs to TypeScript's short-circuiting assignment operators, where a ??= '' is equivalent to a = a ?? ''.
Nevertheless, none of these approaches are as concise as simply using a += b.
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