Clip off last digits from arrays

Question

I have the following array

var arr = ['1234','23C','456','356778', '56']

I want to remove array elements which are less than 3 characters and greater than 4 characters. The final result should be as follows

arr = ['1234', '23C', '456'];  //only 3 and 4 digits in the array. 

Secondly, I want to do the following. if 'arr' has elements longer than 3 characters, I need to clip of by removing the last digit. The final 'data' array should look like this.

arr = ['123', '23C', '456'];

Answer 1

For the first part, you can just use filter to filter out numbers that aren't composed of 3 digits.

var arr = [1234, 234, 456, 356778, 56];
var result = arr.filter(function(num) {
  return num < 1000 && num >= 100;
});

console.log(result);

For the second part, you can use map. Just convert the number to a string. If the length of it is greater than 3, take the substring composed of the first 3 elements of the string, then convert back to a number.

var data = [1234, 123, 4567, 3333];
var result = data.map(function(num) {
  num = num.toString().substring(0, 3);
  return parseInt(num);
});

console.log(result);

Answer 2

All You want is Array.filter and Array.map, and converting String to Number

var arr = [1234,234,456,356778, 56]

var newArr = arr.filter((num) => {
  // convert number to string
  var str = '' + num
  // if length is 3 or 4 - return true (element will be in newArr)
  return str.length === 3 && str.length === 4 
})

and the second case

var newArr = arr.map((num) => {
  var str = '' + num
  // is str is longer than 3, cut it to length of 3
  if(str.length > 3)
    str = str.substring(0, 3)
  // return str converted to number
  return +str
})

Answer 3

To handle if a number is 3 or 4 digits, check if each number is in the range 100 <= num < 10000

  let result = arr.filter(function(val) {
    // is a 3 or 4 digit number
    return 100 >= val && num < 10000;
  });

To clip the four digits to 3 digits, we can divide all four digit numbers by 10 and convert them to an integer

  let clippedResult = result.map(function(val) {
    return val >= 1000 ? Math.floor(val / 10) : val
  });

Answer 4

function filterArray(arr,lowDigits,highDigits){
    var newArr=[];
    for(i=0;i<arr.length;i++){
         val=arr[i];
         length=val.length;
         if(length>=lowDigits&&length<=highDigits){
          if(length>lowDigits){
          val=val.substring(0,lowDigits);
          }
          newArr.push(val);
         }
     }
     return newArr;
}

var arr = ['1234','234','456','356778','56'];
arr=filterArray(arr,3,4);
console.log(arr);

Answer 5

This solution converts the input array to a string of the form 1234,23C,456,356778,56, then finds the wanted elements using regexp.

var arr = ['1234','23C','456','356778', '56'];

console.log(String(arr).match(/\b\w{3}(?=\w?\b)/g));

In English:

Find all the substrings which start with a word boundary (\b, which will be after a comma, or the beginning of the string), then have three alphanumeric characters, and which looking ahead ((?=) may (?) have one additional character before the next word boundary (comma or end of string).

And yes, this will work with string elements, as long as the strings are composed of alphanumerics (in other words, things which won't break the word break (\b) logic.

Answer 6

 let isValidElement = updated_ImportDetails.ImportData.filter(function (num) {
                    // is a 3 or 4 digit number
                    return num.length > 2 && num.length <4 ;
                });




                var result = isValidElement.map(function (num) {
                    num = num.substring(0, 3);
                    return num;
                });

                result = result.filter(function (elem, index, self) {
                    return index == self.indexOf(elem);
                })    //removes duplicates from the array

This worked for me.