Javascript map array then compare keys if statement

Question

I have an array of the alphabet and 2 sets of values, Im trying to check if a value is between the 2 given values then print out the letter. My code:

var alphabet_num = {
"alphabet": ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P"],
"start": ["0", "150", "300", "450", "600", "750", "900", "1050", "1200", "1350", "1500", "1650", "1800", "1950", "2100", "2250"],
"end": ["149", "299", "449", "599", "749", "899", "1049", "1199", "1349", "1499", "1649", "1799", "1949", "2099", "2249", "2399"]
};
var xValue = 76;
var result = alphabet_num.alphabet.map(
(k, i) => [
 k, alphabet_num.start[i], alphabet_num.end[i]
 if (xValue >= alphabet_num.start[i] && xValue <= alphabet_num.end[i]) {
 //a
 }
]
);

• jsN00b: Would you please share the output that is expected?
• Chris: Hi yeah I need the if statement part, so if xValue = 76 then it should check start number and end number then print out the letter A, xValue = 150 then its B etc etc
• Praveen Kumar Yadav: Mao would return you an array of element. Are you sure you want to use map.
• Goran.it: You should use destructuring to obtain conditional array elements. Something like this: ...(cond ? ['a'] : []) . More about that here : 2ality.com/2017/04/conditional-literal-entries.html
• Raeesh Alam: I run this code and getting error .map( (k, i) => [.... so this should be .map( (k, i) => { .... and console result show as you want.

Answer 1

If you are looking for a specific value, you don't need the map function, you could solve it with find.

const result = alphabet_num.alphabet.find(
 (_letter, i) =>
 parseInt(alphabet_num.start[i]) <= xValue &&
 xValue <= parseInt(alphabet_num.end[i])
);

Answer 2

<script>
var alphabet_num = {
"alphabet": ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P"],
"start": ["0", "150", "300", "450", "600", "750", "900", "1050", "1200", "1350", "1500", "1650", "1800", "1950", "2100", "2250"],
"end": ["149", "299", "449", "599", "749", "899", "1049", "1199", "1349", "1499", "1649", "1799", "1949", "2099", "2249", "2399"]
};
var xValue = 350;
var result = alphabet_num.alphabet.map(
 function(k, i){
 if (xValue >= alphabet_num.start[i] && xValue <= alphabet_num.end[i]) {
 console.log(alphabet_num.alphabet[i]);
 return alphabet_num.alphabet[i];
 }else{
 return '0';
 }
 }
);
// with 350 the array result
// result = ['0', '0', 'C', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0']
console.log(result);
// user findIndex function to find indx
let index = result.findIndex(function (value){
 return value!='0';
});
// the index of 'C' letter in array result index =2
console.log(index);
// get result[2] so I get 'C' letter
console.log(result[index]);
</script>

• Ziur Olpa: Thanks for your answer, don't forget to include a short description, welcome to SO!

Answer 3

You can use this

 alphabet_numBetweenStartAndEnd = function (alphabet_num, xValue) {
 for (var i = 0; i < alphabet_num.start.length; i++) {
 if (xValue >= alphabet_num.start[i] && xValue <= alphabet_num.end[i]) {
 return alphabet_num.alphabet[i];
 }
 }
}