JS create new array with cumulative numbers last index without reorder

Question

how to create new array with cumulative numbers last index to next cumulative first index.

I have an array-like

const numbers = [ '1',   '2',   '3',   '16',  '17',  '18',  '19',  '31',  '32', '42',  '43',  '53',  '54',  '58',  '59',  '69',  '70',  '81', '82',  '103', '104', '115', '116']

The expected output will be like

const newArray = [['3', '16'], ['19','31'], ['32','42'], ['43', '53'] ... ]

There is always at least two cumulative number. I tried

const numbers = ['1', '2', '3', '16', '17', '18', '19', '31', '32', '42', '43', '53', '54', '58', '59', '69', '70', '81', '82', '103', '104', '115', '116']

const reGroup = []

const findGroup = numbers.reduce((prev, current) => {
  data = []
  if (prev == (current - 1)) {
    data.push(prev, current)
  }
  reGroup.push(data)
})
console.log(reGroup)

Louys Patrice Bessette · Accepted Answer · 2022-01-30 21:56:22Z

3

A forEach loop should do. You just have to keep the previous number on hand for comparison.

See comments within the code below.

const numbers = [ '1', '2', '3', '16', '17', '18', '19', '31', '32', '42', '43', '53', '54', '58', '59', '69', '70', '81', '82', '103', '104', '115', '116']

let previous = 0;
let result = [];

// Loop though each array item
numbers.forEach(number => {
  // Have it as a number
  number = parseInt(number);

  // If the previous number + 1 does not equal this one
  if (previous + 1 != number) {
    // Push a sub array containing the previous number and this one (to string)
    result[result.length] = [previous.toString(), number.toString()];
  }

  // Save the current number for the next iteration
  previous = number;
});

/* The expected output will be like
        [['3', '16'], ['19','31'], ['32','42'], ['43', '53'] ... ]
    */
console.log(result);

edited Jan 30, 2022 at 21:56

answered Jan 30, 2022 at 21:46

Louys Patrice Bessette

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Comments

ManuelMB · Accepted Answer · 2022-01-30 21:45:17Z

0

const numbers = ['1', '2', '3', '16', '17', '18', '19', '31', '32', '42', '43', '53', '54', '58', '59', '69', '70', '81', '82', '103', '104', '115', '116']
let newArray = []
for(i=0; i < numbers.length; i+=2){
   const element = numbers.slice(0 + i, i +2)
   newArray.push(element)
}

console.log(newArray)

0: (2) ['1', '2']

1: (2) ['3', '16']

2: (2) ['17', '18']

3: (2) ['19', '31']

4: (2) ['32', '42']

5: (2) ['43', '53']

6: (2) ['54', '58']

7: (2) ['59', '69']

8: (2) ['70', '81']

9: (2) ['82', '103']

10: (2) ['104', '115']

answered Jan 30, 2022 at 21:45

ManuelMB

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