根据多个属性对对象数组进行排序

Question

I'm trying to sort array of objects based on arbitrary property inside the object. I wrote the following code which works perfectly.

var customSort = function(data, sortBy, order) {
  if (!(data && sortBy)) {
    throw new Error('Specify the data source and atleast one property to sort it by');
  }
  if (!Array.isArray(data)) {
    throw new Error('Specify the data source as an array');
  }
  order = order || 'asc';

  function performSort(order, sortBy) {
    return data.sort(function(a, b) {
      var A = parse(a, sortBy);
      var B = parse(b, sortBy);
      if (A < B) {
        return order === 'asc' ? -1 : 1;
      } else if (A > B) {
        return order === 'asc' ? 1 : -1;
      } else {
        return 0;
      }
    });
  }

  function parse(data, sortBy) {
    var sortParams = sortBy.split('.');
    var latestValue = data;
    for (var i = 0; i < sortParams.length; i++) {
      latestValue = latestValue[sortParams[i]];
    }
    if (!latestValue) {
      throw new Error('Check the \'sortBy\' parameter. Unreachable parameter in \'sortBy\'');
    }
    if (typeof latestValue === 'string') {
      return latestValue.toLowerCase();
    } else {
      return latestValue;
    }
  }

  return performSort(order, sortBy);
};

var lonelyData = [{
  a: {
    b: 2
  }
}, {
  a: {
    b: 1
  }
}, {
  a: {
    b: 9
  }
}, {
  a: {
    b: 7
  }
}, {
  a: {
    b: 4
  }
}, {
  a: {
    b: 2
  }
}, {
  a: {
    b: 1
  }
}];

console.log(customSort(lonelyData, 'a.b'));

Fiddle here: JSFiddle



Now, I'm trying to use recursion to have sort by multiple properties in following manner: First, sort by first property and then within that same property, sort by second property, and so on. For keeping things simple, I'm assuming same order for all the properties, ie either all increasing or all decreasing.
I wrote this code:

var customSort = function(data, sortBy, order) {
  if (!(data && sortBy)) {
    throw new Error('Specify the data source and atleast one property to sort it by');
  }
  if (!Array.isArray(data)) {
    throw new Error('Specify the data source as an array');
  }
  if (!Array.isArray(sortBy)) {
    sortBy = [sortBy];
  }
  order = order || 'asc';

  function performSort(order, sortBy) {
    return data.sort(function(a, b) {
      function nestedSort() {
        var highestOrder = sortBy[0];
        var A = parse(a, highestOrder);
        var B = parse(b, highestOrder);
        if (A < B) {
          return order === 'asc' ? -1 : 1;
        } else if (A > B) {
          return order === 'asc' ? 1 : -1;
        } else {
          sortBy.shift();
          nestedSort();
        }
      }
      return nestedSort();
    });
  }

  function parse(data, sortBy) {
    var sortParams = sortBy.split('.');
    var latestValue = data;
    for (var i = 0; i < sortParams.length; i++) {
      latestValue = latestValue[sortParams[i]];
    }
    if (!latestValue) {
      throw new Error('Check the \'sortBy\' parameter. Unreachable property passed in \'sortBy\'');
    }
    if (typeof latestValue === 'string') {
      return latestValue.toLowerCase();
    } else {
      return latestValue;
    }
  }

  return performSort(order, sortBy);
};

var lonelyData = [{
  a: {
    b: 2,
    c: 'Z'
  }
}, {
  a: {
    b: 2,
    c: 'A'
  }
}, {
  a: {
    b: 9,
    c: 'Q'
  }
}, {
  a: {
    b: 7,
    c: 'L'
  }
}, {
  a: {
    b: 7,
    c: 'E'
  }
}, {
  a: {
    b: 1,
    c: 'A'
  }
}, {
  a: {
    b: 1,
    c: 'B'
  }
}];

console.log(customSort(lonelyData, ['a.b', 'a.c']));

Fiddle here: JSFiddle


Unfortunately, I couldn't make it work. What am I missing here?

Answer 1

  sortBy.shift(); nestedSort(); 

is your problem. shift does mutate the array, and drop the first item forever. The next time the comparison function is called to compare a with b , it will be ignored, and soon the array will be empty and your comparsion breaks completely.

Instead, use a simple loop:

return data.sort(function(a, b) {
  for (var i=0; i<sortBy.length; i++)
    var currentOrder = sortBy[i];
    var A = parse(a, currentOrder);
    var B = parse(b, currentOrder);
    if (A < B) {
      return order === 'asc' ? -1 : 1;
    } else if (A > B) {
      return order === 'asc' ? 1 : -1;
    }
  }
  return 0;
});