将值分配给新数组

Question

I am new to associative arrays and I have this code below. I would like to assign the values for prop and sumprop[prop] to a new array, prop1 and prop2 . Appreciate some help here.

var name = new Array();
var amount = new Array();

name[0]="Peter";
amount[0]="50";
name[1]="John";
amount[1]="10";
name[2]="John";
amount[2]="20";
name[3]="Peter";
amount[3]="20";
name[4]="Mary";
amount[4]="40";

var sum = {};
var i;
var prop1 = new Array();
var prop2 = new Array();

for (i = 0; i < amount.length; i++) {
  var name = name[i];
  var oldSum = sum[name];
  if (typeof oldSum === 'undefined') {
    oldSum = 0;
  }
  sum[name] = oldSum + amount[i];
} 

for (var prop in sum) {
  if (sum.hasOwnProperty(prop)) {
    console.log(prop + " " sum[prop]);
    // assign to a new array
  }
}

Answer 1

I rewrote your code to make your intentions more clear (using better variable names and changing the data's structure):

var people = [
    { name: 'Peter', amount: 50 },
    { name: 'John', amount: 10 }
    // etc.    
];

var sums = {};
var i, person;

for (i = 0; i < people.length; i++) {
  person = people[i];
  if (typeof sums[person.name] === 'undefined') {
    sums[person.name] = 0;
  }
  sums[person.name] += person.amount;
} 

for (var name in sums) {
  if (sums.hasOwnProperty(name)) {
    console.log(name, sums[name]);
  }
}​

Your trying to force arrays to act like dictionaries, which is an uphill battle. You also don't need to use the array constructor (ie new Array() ) because you can just create a new array like this var someVar = []; .

Answer 2

You probably want:

for (var prop in sum) {
  if (sum.hasOwnProperty(prop)) {

     prop1.push(prop);
     prop2.push(sum[prop]);

  }
}

Answer 3

You want this:

for (var prop in sum) {
  console.log(prop + " " sum[prop]);
  prop1.push(prop);
  prop2.push(sum[prop])
}

Also, don't use new Array() when initializing arrays, use:

var prop1 = [];