I have an array where I want to check for all instances of a specific letter where there are empty values in-between, or they are adjacent.
let myArray1 = ['A',,,,,'A'] //function returns [0,5]
let myArray2 = ['A',,,'E',,'A'] //function returns []
let myArray3 = [,,'A',,'A','G'] //function returns [2,4]
let myArray4 = [,,'A','A','G'] //function returns [2,3]
let myArray5 = [,,'A','A','G','A'] //function returns [2,3]
I've been trying with a for loop and push to array but I'm getting muddled.
Any ideas on how to do this function?
You could use .findIndex() to find the first non empty value (ie: character) and its index in your array. You can then use .findIndex() again on your array to find the second non-empty value that appears after your first character. If the first character and the second character match then you can return the indexes, otherwise you can return an empty array:
const getRange = (arr) => {
const first = arr.findIndex(c => c !== undefined);
const second = arr.findIndex((c, i) => i !== first && c !== undefined);
return first !== -1 && arr[first] === arr[second] ? [first, second] : [];
}
console.log(getRange([,,,,,]));
console.log(getRange(['A',,,,,'A']));
console.log(getRange(['A',,,'E',,'A']));
console.log(getRange([,,'A',,'A','G']));
console.log(getRange([,,'A','A','G']));
console.log(getRange([,,'A','A','G','A']));To optimize, you can do this with one-pass using a regular for..of loop by iterating the .entries() of the array;
const getRange = (arr) => {
let first = -1;
let second = -1;
for(const [i, char] of arr.entries()) {
if(char !== undefined && first === -1)
first = i;
else if(char !== undefined && second === -1)
second = i;
}
return first !== -1 && arr[first] === arr[second] ? [first, second] : [];
}
console.log(getRange([,,,,,]));
console.log(getRange(['A',,,,,'A']));
console.log(getRange(['A',,,'E',,'A']));
console.log(getRange([,,'A',,'A','G']));
console.log(getRange([,,'A','A','G']));
console.log(getRange([,,'A','A','G','A']));function getMyResult(itemToSearch, array) {
var firstIndex;
var secondIndex;
for (var i = 0; i < array.length; i++) {
if (array[i] == itemToSearch) {
if (firstIndex == null)
firstIndex = i;
else {
secondIndex = i;
break; // break loop as we got two success indices
}
} else if (array[i] != null) {
if (firstIndex != null) {
// something got in between the items
break;
}
}
}
if (firstIndex != null && secondIndex != null)
return [firstIndex, secondIndex]; // success indices
return []; //not success
}
let myArray1 = ['A',,,,,'A'];
let myArray2 = ['A',,,'E',,'A']; //function returns []
let myArray3 = [,,'A',,'A','G']; //function returns [2,4]
let myArray4 = [,,'A','A','G']; //function returns [2,3]
let myArray5 = [,,'A','A','G','A']; //function returns [2,3]
console.log(
getMyResult('A', myArray1)
);
console.log(
getMyResult('A', myArray2)
);
console.log(
getMyResult('A', myArray3)
);
console.log(
getMyResult('A', myArray4)
);
console.log(
getMyResult('A', myArray5)
);The above function getMyResult will solve your problem.
You can use for loop to keep track of last value and its index, if last value is same as current value you can break the loop otherwise you can reset last value and start index.
const getRange = (arr) => {
let last = '', start = -1, end = -1;
for(let i = 0; i < arr.length; i++) {
if(arr[i]) {
if(last === arr[i]) {
end = i;
break;
} else {
start = i;
last = arr[i];
}
}
}
return end !== -1 ? [start, end]: []
}
console.log(getRange(['A',,,,,'A']));
console.log(getRange(['A',,,'E',,'A']));
console.log(getRange([,,'A',,'A','G']));
console.log(getRange([,,'A','A','G']));
console.log(getRange([,,'A','A','G','A']));
console.log(getRange([,,,'E',,'E',,,,,'E']));
console.log(getRange([,,'A',,'G','A',,,,,'A']));
console.log(getRange(['A',,,'E',,'A']));