comparator-chain.js

function getPath(object, path) {
  if (typeof object === 'undefined' || typeof path !== 'string') {
    return undefined;
  }

  var index = path.trim().indexOf('.');
  if (index < 0) {
    return object[path];
  }

  var key = path.substr(0, index);
  var next = path.substr(index + 1);
  return getPath(object[key], next);
}

// const people = [{
//   name: "bob",
//   title: "bossA",
//   age: 42
// },{
//   name: "bob",
//   title: "boss",
//   age: 42
// }]; 
// people.sort((a, b) => new ComparatorChain(
//     "+age", 
//     "+name",
//     "+title")
// .compare(a, b));
// console.log(JSON.stringify(people, null, 2));


const ASCENDING = "+";
const DESCENDING = "-";
const EQUAL = 0;
const BEFORE = -1;
const AFTER = 1;

class ComparatorChain {
  constructor(...properties) {
    this.properties = Array.from(properties)
      .map(property => this._parseProperty(property));
  }
  
  _parseProperty(property) {
    if (_.isFunction(property)) {
      return property;
    }
    
    const direction = property.charAt(0);
    const hasDirection = direction === ASCENDING || direction === DESCENDING;
    return {
      direction: hasDirection ? direction : ASCENDING,
      propertyName: hasDirection ? property.slice(1) : property
    };    
  }
  
  compare(a, b) {
    let result = EQUAL;
    
    for (const property of this.properties) {
      if (_.isFunction(property)) {
        result = property.call(this, a, b);
      } else {
        result = this.compareProperty(a, b, property);
      }
      
      if (result !== EQUAL) {
        break;
      }
    }
    return result;
  }
  
  compareProperty(a, b, { propertyName, direction }) {
    // const propertyA = Ember.get(a, propertyName);
    // const propertyB = Ember.get(b, propertyName);
    const propertyA = getPath(a, propertyName);
    const propertyB = getPath(b, propertyName);
    
    if (propertyA === propertyB) {
      return EQUAL;
    }


    if (direction === ASCENDING) {
      return propertyA > propertyB ? AFTER : BEFORE;
    }
    return propertyA < propertyB ? AFTER : BEFORE;
  }
}