Javascript : make function parameter required

 

function checkParam() {

   throw new Error('Parameter is required');

}

function myFunction(param=checkParam()) {

   console.log(param);

}

myFunction('Hello'); // Output: Hello

myFunction(); // Throws an error: Parameter is required

Output:

Hello

C:\Users\sangr\Practice\paramRequired.js:2

   throw new Error('Parameter is required');

   ^

Error: Parameter is required

    at checkParam (C:\Users\sangr\Practice\paramRequired.js:2:10)

    at myFunction (C:\Users\sangr\Practice\paramRequired.js:5:27)

    at Object.<anonymous> (C:\Users\sangr\Practice\paramRequired.js:11:1)

    at Module._compile (node:internal/modules/cjs/loader:1734:14)

    at Object..js (node:internal/modules/cjs/loader:1899:10)

    at Module.load (node:internal/modules/cjs/loader:1469:32)

    at Function._load (node:internal/modules/cjs/loader:1286:12)

    at TracingChannel.traceSync (node:diagnostics_channel:322:14)

    at wrapModuleLoad (node:internal/modules/cjs/loader:235:24)

    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:151:5)

Node.js v23.9.0

Explanation:

In this code, we define a function `checkParam()` that throws an error if it is called.

The `myFunction()` function takes a parameter `param`, which defaults to the result

of calling `checkParam()`. If `myFunction()` is called without an argument,

`checkParam()` is invoked, resulting in an error being thrown. If `myFunction()` is

called with an argument, it simply logs that argument to the console.