Javascript当为null时跳到下一个记录代码修改

Question

I have some code that's working great but I have a problem with.

Basically when it get to a record that's NULL it's adding a 0 to the array...

In this case the second record is NULL, so I'm getting:

[10, 0, 20]

What I need it to do is that if thsub is NULL then add nothing to the array and continue to the next record.

So the desired result in this case would be:

[10, 20]

Here's the full code:

 var data = { "cars": [{ "id": "1", "name": "name 1", "thsub": [{ "id": "11", "name": "sub 1", "stats": { "items": 5, }, "ions": null }, { "id": "22", "name": "sub 2", "stats": { "items": 5, }, "translations": null }], "image": null }, { "id": "2", "name": "name 2", "thsub": null, //this will break the code "image": null }, { "id": "54", "name": "name something", "thsub": [{ "id": "65", "name": "sub 1", "stats": { "items": 10, }, "ions": null }, { "id": "22", "name": "sub 2", "stats": { "items": 10, }, "translations": null }], "image": null } ] } var thCount = []; for (var l = 0, m = data.cars.length; l < m; l++) { thCount[l] = 0; if (data.cars[l].thsub) { for (var i = 0, j = data.cars[l].thsub.length; i < j; i++) { if (data.cars[l].thsub[i].stats) { thCount[l]+=data.cars[l].thsub[i].stats.items; } } } } console.log(thCount); 

How can I do this?

Answer 1

You could push only a value, if thsub is set.

 var data = { cars: [{ id: "1", name: "name 1", thsub: [{ id: "11", name: "sub 1", stats: { items: 5, }, ions: null }, { id: "22", name: "sub 2", stats: { items: 5, }, translations: null }], image: null }, { id: "2", name: "name 2", thsub: null, image: null }, { id: "54", name: "name something", thsub: [{ id: "65", name: "sub 1", stats: { items: 10, }, ions: null }, { id: "22", name: "sub 2", stats: { items: 10, }, translations: null }], image: null }] }, thCount = []; for (var l = 0, m = data.cars.length; l < m; l++) { if (data.cars[l].thsub) { thCount.push(0); for (var i = 0, j = data.cars[l].thsub.length; i < j; i++) { if (data.cars[l].thsub[i].stats) { thCount[thCount.length - 1] += data.cars[l].thsub[i].stats.items; } } } } console.log(thCount); 

Answer 2

solution

you need to add variable and then push to array only if there is something.

var data = {
  "cars": [{
      "id": "1",
      "name": "name 1",
      "thsub": [{
        "id": "11",
        "name": "sub 1",
        "stats": {
          "items": 5,
        },
        "ions": null
      }, {
        "id": "22",
        "name": "sub 2",
        "stats": {
          "items": 5,
        },
        "translations": null
      }],
      "image": null
    },

    {
      "id": "2",
      "name": "name 2",
      "thsub": null, //this will break the code
      "image": null
    },
    {
      "id": "54",
      "name": "name something",
      "thsub": [{
        "id": "65",
        "name": "sub 1",
        "stats": {
          "items": 10,
        },
        "ions": null
      }, {
        "id": "22",
        "name": "sub 2",
        "stats": {
          "items": 10,
        },
        "translations": null
      }],
      "image": null
    }
  ]
}



var thCount = [];

for (var l = 0, m = data.cars.length; l < m; l++) {
  if (data.cars[l].thsub) {
    var tmp = 0;
    for (var i = 0, j = data.cars[l].thsub.length; i < j; i++) {
      if (data.cars[l].thsub[i].stats) {
        tmp+=data.cars[l].thsub[i].stats.items;
      }
      thCount.push(tmp);
    }
  }
}

console.log(thCount);

Answer 3

You can create new variable inside for loop and use push() instead if its not 0.

 var data = {"cars":[{"id":"1","name":"name 1","thsub":[{"id":"11","name":"sub 1","stats":{"items":5},"ions":null},{"id":"22","name":"sub 2","stats":{"items":5},"translations":null}],"image":null},{"id":"2","name":"name 2","thsub":null,"image":null},{"id":"54","name":"name something","thsub":[{"id":"65","name":"sub 1","stats":{"items":10},"ions":null},{"id":"22","name":"sub 2","stats":{"items":10},"translations":null}],"image":null}]} var thCount = []; for (var l = 0, m = data.cars.length; l < m; l++) { var count = 0 if (data.cars[l].thsub) { for (var i = 0, j = data.cars[l].thsub.length; i < j; i++) { if (data.cars[l].thsub[i].stats) { count += data.cars[l].thsub[i].stats.items; } } } if (count != 0) thCount.push(count) } console.log(thCount); 

Answer 4

The line thCount[l] = 0; will cause to add an element to thCount regardless of your condition if (data.cars[l].thsub)

You can use another variable and increase it only when we want to add something to our array:

  var data = { "cars": [{ "id": "1", "name": "name 1", "thsub": [{ "id": "11", "name": "sub 1", "stats": { "items": 5, }, "ions": null }, { "id": "22", "name": "sub 2", "stats": { "items": 5, }, "translations": null }], "image": null }, { "id": "2", "name": "name 2", "thsub": null, //this will break the code "image": null }, { "id": "54", "name": "name something", "thsub": [{ "id": "65", "name": "sub 1", "stats": { "items": 10, }, "ions": null }, { "id": "22", "name": "sub 2", "stats": { "items": 10, }, "translations": null }], "image": null } ] } var thCount = []; for (var l = 0, k = -1, m = data.cars.length; l < m; l++) { if (data.cars[l].thsub) { thCount[++k] = 0; for (var i = 0, j = data.cars[l].thsub.length; i < j; i++) { if (data.cars[l].thsub[i].stats) { thCount[k] += data.cars[l].thsub[i].stats.items; } } } } console.log(thCount); //alert(thCount); 

Answer 5

There has been some answers about how to fix the loop, so the basic problem is with the thCount[l] = 0 line. You can also use higher order functions to loop through the object which results in a better readable code in my opinion:

 var data = { "cars": [{ "id": "1", "name": "name 1", "thsub": [{ "id": "11", "name": "sub 1", "stats": { "items": 5, }, "ions": null }, { "id": "22", "name": "sub 2", "stats": { "items": 5, }, "translations": null }], "image": null }, { "id": "2", "name": "name 2", "thsub": null, //this will break the code "image": null }, { "id": "54", "name": "name something", "thsub": [{ "id": "65", "name": "sub 1", "stats": { "items": 10, }, "ions": null }, { "id": "22", "name": "sub 2", "stats": { "items": 10, }, "translations": null }], "image": null } ] } var thCount = data.cars.filter(function(car){ return car.thsub; }).map(function(car){ return car.thsub.reduce(function(a,b){ return a.stats.items + b.stats.items; }); }); console.log(thCount) 

First, you filter out all objects that have no thsub . Then you map those entries to new values. You get those values with the reduce -function, which sums up all the items -values in the stats .

Answer 6

One also might consider a nested reduce approach eg like the following ...

 var data = { "cars": [{ "id": "1", "name": "name 1", "thsub": [{ "id": "11", "name": "sub 1", "stats": { "items": 5 }, "translations": null }, { "id": "22", "name": "sub 2", "stats": { "items": 5 }, "translations": null }], "image": null }, { "id": "2", "name": "name 2", "thsub": null, "image": null }, { "id": "54", "name": "name something", "thsub": [{ "id": "65", "name": "sub 1", "stats": { "items": 10 }, "translations": null }, { "id": "22", "name": "sub 2", "stats": { "items": 10 }, "translations": null }], "image": null }] }; var thCount = data.cars.reduce(function (collector, carItem) { var thSubs = carItem.thsub; //if (Array.isArray(thSubs)) { ... } if ((thSubs != null) && (thSubs.length >= 1) && Number.isFinite(thSubs.length)) { collector.push( thSubs.reduce(function (count, subItem) { return (count + subItem.stats.items); }, 0) ); } return collector; }, []); console.log(thCount);