TypeScript: 检查变量是否为 Null 或 Undefined

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typescript 变量 null 或者空判断

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在 JavaScript 的数据处理过程中，希望了解下如果对变量进行空的字符串判断。

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It looks like there aren’t any topics currently discussing the TypeScript null or empty check on iSharkFly. However, I can help you with the general approach.

In TypeScript, you can check if a variable is null or undefined (which might be what you mean by “empty”) using a few common methods:

  1. Using the strict equality (===) operator:

    • You can directly check if a variable is null or undefined.
    if (variable === null || variable === undefined) {
    console.log("The variable is null or undefined.");
}

  2. Using the loose equality (==) operator:

    • This is a shorter form where null loosely equals undefined.
    if (variable == null) { // covers both null and undefined
    console.log("The variable is null or undefined.");
}

  3. Using the optional chaining (?.) with nullish coalescing operator (??):

    • Useful for deep object property checks or providing default values.
    const value = obj?.prop ?? "default value"; // if obj or prop is null/undefined, return "default value"

If you have a specific scenario or code example you’re working with, I can give more tailored advice!