MergeSort

MergeSort.js

const _ = require('underscore');

class MergeSort {
  
  sort(arr) {
    if(arr.length === 1) {
      return arr;
    }
    
    const half = Math.floor(arr.length / 2);
    const left = arr.slice(0, half);
    const right = arr.slice(half, arr.length);
    
    return this.merge(this.sort(left), this.sort(right));
  }
  
  merge(left, right) {
    let result = [];
    
    while (left.length > 0 || right.length > 0) {
      if (left.length > 0 && right.length > 0) {
        if (left[0] < right[0]) {
          result.push(left.shift());
        } else {
          result.push(right.shift()); 
        }
      } else if (left.length > 0) {
        result.push(left.pop()) 
      } else {
        result.push(right.pop()) 
      }  
    }
    
    return result;
  }
  
}

const test = (currentResult, expectedResult) => {
  if (!_.isEqual(currentResult, expectedResult)) {
    console.log('Error!');
  } else {
    console.log('Success.');
  }
} 

var obj = new MergeSort();

test(obj.sort([10,1,3,11]), [1,3,10,11]);