I'm trying to check an array to see if only one of the elements has data. For example this is my array:
playersByGender = {
mens: [],
womens: [],
other: []
};
Any combo of these can have data as well as only one. How would I check all three and return a boolean on if only one is filled out?
I thought about using a foreach but you're not able to do that on an object.
Any help would be great, thanks!
Iterate the object's keys with Array#reduce, and for every array with length > 0, add 1 to the sum. Compare the final sum to get a Boolean answer.
const playersByGender = {
mens: [],
womens: [1, 2],
other: []
};
const onlyOne = (obj) => Object.keys(obj).reduce((sum, k) => obj[k].length > 0 ? sum + 1 : sum, 0) === 1;
console.log(onlyOne({
mens: [],
womens: [1, 2],
other: []
}));
console.log(onlyOne({
mens: [],
womens: [1, 2],
other: [1]
}));
Operator '+' cannot be applied to types 'number' and 'boolean'.let playersByGender = {
mens: [],
womens: [1,1],
other: []
};
console.log(Object.values(playersByGender).filter(a => a.length > 0).length === 1);Object.values returns the array of all object values, then we leave only filled arrays and count them: .filter(a => a.length > 0).length
You're looking for a for in loop as oppose to foreach. With the for in loop you can look over your object properties, measure the length and return if any of the object's arrays have a length.
Only 1:
var playersByGender = {
mens: [1],
womens: [],
other: []
},
oneArrayLength = false;
for(var key in playersByGender) {
if(playersByGender.hasOwnProperty(key)) {
if(playersByGender[key].length) {
if(!oneArrayLength) {
oneArrayLength = true;
} else {
oneArrayLength = false;
break;
}
}
}
}
console.log(oneArrayLength);More than 1:
var playersByGender = {
mens: [1],
womens: [1],
other: []
},
oneArrayLength = false;
for(var key in playersByGender) {
if(playersByGender.hasOwnProperty(key)) {
if(playersByGender[key].length) {
if(!oneArrayLength) {
oneArrayLength = true;
} else {
oneArrayLength = false;
break;
}
}
}
}
console.log(oneArrayLength);Edit:
I changed the above solution to match what you described in your question of only returning true when 1 of the arrays has values.
You can loop over the arrays, see how many are in each one, then filter out the ones that don't have any, then count them. There are lots of ways to do this as others have mentioned. I think all the answers show different methods of how you could do it. You should familiarize yourself with all the methods available to Arrays. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
Here is another option with explanation:
let arraysWithMoreThanOne = Object.keys(playerByGender).map(function(key) {
// starting with an array of keys men, women, other
// the map method allows us to convert the key into something else.
// in this case, the length of the array
// we only care about the lengths
return playersByGender[key].length;
}).filter(function(count) {
// filter allows us to discard item in an array we don't care about
// we only care if they have more than 1 in them
return count > 0;
}) // at the end, we have converted the object into a different result
.length; // this is the number of arrays that had more than one item
Depending on your environment, some methods need polyfills to support.
You could indeed use a for..in loop like this:
function oneArrayHasData(arr) {
var dataExists = false;
for (var prop in arr) {
if (playersByGender[prop].length) dataExists = true;
}
return dataExists;
}
var dataFound = oneArrayHasData(playersByGender);
