Can you explain the significance of a variable name with a question mark? For example:
Label?: string
I've noticed this syntax in various instances but am unsure about its meaning.
Can you explain the significance of a variable name with a question mark? For example:
Label?: string
I've noticed this syntax in various instances but am unsure about its meaning.
? denotes that the parameter is optional in TypeScript specifically. Unlike JavaScript, where all parameters are optional by default, this feature allows for more precise control over function inputs.
According to the Typescript official documentation,
In JavaScript, every parameter is optional and can be omitted at will, with the value defaulting to undefined. In TypeScript, we can replicate this behavior by appending a ? to the end of parameters intended to be optional.
function buildName(firstName: string, lastName?: string) {
if (lastName)
return firstName + " " + lastName;
else
return firstName; }
let result1 = buildName("Bob"); // executes correctly
let result2 = buildName("Bob", "Adams", "Sr."); // error due to excess parameters
let result3 = buildName("Bob", "Adams"); // exact match
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