I am trying to recreate the indexOf function in JavaScript. I can not get the return -1 portion to work, but the other parts work fine. It seems like the end of my for loop is not running, as I try to print out "end of loop". I have some test code as well and the outputs below. Any help would be appreciated.
Array.prototype.myIndexOf = function(...args) {
if(args[1] === undefined){
for(let i = 0; i < this.length; i++){
if(this[i] === args[0]){
return i;
}
}
} else {
for(let i = args[1]; i < this.length; i++){
if(this[i] === args[0]){
return i;
}
}
console.log("end of loop")
return -1;
}
};
// TEST
const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];
console.log(beasts.indexOf('bison'));
console.log(beasts.myIndexOf('bison'));
// expected output: 1
// start from index 2
console.log(beasts.indexOf('bison', 2));
console.log(beasts.myIndexOf('bison', 2));
// expected output: 4
console.log(beasts.indexOf('giraffe'));
console.log(beasts.myIndexOf('giraffe'));
// expected output: -1
1
1
4
4
-1
undefined
You're close. Move the return -1; statement outside of the if/else blocks. As it's currently written, you'll only receive the -1 if it doesn't find a match and you passed in two arguments.
Array.prototype.myIndexOf = function(...args) {
if(args[1] === undefined){
for(let i = 0; i < this.length; i++){
if(this[i] === args[0]){
return i;
}
}
} else {
for(let i = args[1]; i < this.length; i++){
if(this[i] === args[0]){
return i;
}
}
}
return -1;
};
// TEST
const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];
console.log(beasts.indexOf('bison'));
console.log(beasts.myIndexOf('bison'));
// expected output: 1
// start from index 2
console.log(beasts.indexOf('bison', 2));
console.log(beasts.myIndexOf('bison', 2));
// expected output: 4
console.log(beasts.indexOf('giraffe'));
console.log(beasts.myIndexOf('giraffe'));
// expected output: -1With this change, you will always hit return -1; if there is no match regardless of the number of parameters passed in.
In the last test case you are not sending a second argument to the function, so it is the first part of the if-else that will run - the if part. There is no return -1 in that part.