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Are you having issues Setting optional parameters in Functions using TypeScript? Don’t worry about it! This post will teach you about the characteristics of optional parameters and provide some fixes. Let’s get going!
The way to Setting optional parameters in Functions using TypeScript
Before learning to set it using TypeScript, we will give you some base information about optional parameters.
The optional parameter is defined in typescript as a parameter that can be constructed optional while passing the values when the function is called, and the values that are passed when the process is called are printed without errors.
Overall, as the name implies, we can make the parameters of the function optional for passing values when the process is called without errors, and typescript supports this feature.
Utilize the? Symbol behind the parameter name
When a parameter’s value or specification is not required, we utilize optional parameters. To make a function argument optional, we add the question mark (“?”) after the parameter name. Similar to rest parameters, optional parameters need to come after the primary or necessary parameters in order to avoid errors.
To answer the article question, there will be three steps.
Step 1: Utilize the ? symbol behind the c parameter.
Step 2: Use the expression typeof c!== ‘undefined’ to see whether the argument was passed to the function.
That will have the syntax as:
<parameter-name>? : <parameter-type>
Take a look at the example below:
function multiply(a: number, b: number, c?: number): number {
if (typeof c !== 'undefined') {
return a * b * c;
}
return a * b;
}
The optional parameters should always come after the required parameters in the parameter list. The TypeScript compiler will generate an error if you make the b parameter optional and the c parameter needed. As an example:
function multiply(a: number, b?: number, c: number): number {
if (typeof c !== 'undefined') {
return a * b * c;
}
return a * b;
}
The command’s output will be:
error TS1016: A required parameter cannot follow an optional parameter.
Step 3: Determine whether we pass the parameter value. If the output looks like this, we haven’t given it yet.
function getSchool(name: string, address?: string, pinCode?: string): string {
if (address == undefined) {
console.log('address not defined');
}
if (pinCode == undefined) {
console.log('pincode not defined');
}
//...
}
The error occurs due to the failure to provide an argument for a parameter whose value is set to undefined by default.
Conclusion
ITtutoria hopes you’ve discovered the most effective method for setting optional parameters in functions using TypeScript. We also hope that explains the mistake you ran into and, ideally, offers a few more ways to prevent it. Please comment below if you run into any additional problems with this question, and we’ll get back to you as soon as possible! We appreciate your reading.
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