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JavaScript Tip: Throw an Error if a Required Parameter Is Missing

Michael Hoffmann - Senior Frontend Developer (Freelancer)
Michael Hoffmann
Dec 26, 2022
1 min read
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428 views
Javascript
JavaScript Tip: Throw an Error if a Required Parameter Is Missing Image

Default function parameters allow named parameters to be initialized with default values if no value or undefined is passed.

We can use this approach to write a function that throws an error if a required parameter is missing:

index.js
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const isRequired = () => {
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throw new Error('Parameter is required!')
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}
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const foo = (bar = isRequired()) => {
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console.log(bar)
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}
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foo() // throws the isRequired error
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foo(undefined) // throws the isRequired error
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foo(false) // logs "false"
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foo(null) // logs "null"
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foo('Test') // logs "true"

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