Is there a way to create a function that only returns strings? For context, I was trying to create the function attached as a screenshot, with the aim of concatenating two strings and returning another string. However, the function also worked on numbers, as it added them. In some cases, I would only want the function to work on a particular data type. Is this possible?
function concatenate(a,b) {
return (a+b);
}
So you either convert them the types you want
function example (a, b) {
return a.toString() + b.toString();
}
console.log(example("foo", "bar"));
console.log(example(1, 2));Or you do validation on the types
function example (a, b) {
if (typeof a !== "string" || typeof b !== "string" ) {
throw new Error("Strings expected");
}
return a + b;
}
console.log(example("foo", "bar"));
console.log(example(1, 2));If you really care about string vs String
if (
!(typeof a === 'string' || a instanceof String) ||
!(typeof b === 'string' || b instanceof String)) {
throw new Error("Strings expected");
}
Generic function can be created accepting the type and it can return function making all validations which can be used to perform action.
function GenericConcat(typeA,typeB) {
return (a,b) => {
if (typeof a == typeA && typeof b == typeB ) {
return a + b;
}
throw new Error("Parameter type expected: "+ typeA +"-"+ typeB);
}
}
stringConcate = GenericConcat("string","string");
stringConcate("a","b"); //ab
stringConcate("a",1) //Error: Parameter type expected: string-string
numberConcate = GenericConcat("number","number");
numberConcate(1,2); //3
numberConcate("a",1); //Error: Parameter type expected: number-number
GenericConcat("string","string")("A","B");
GenericConcat("number","number")(1,2);