Javascript to validate json message

Question

I'm working to keep validation to the incoming json message mentioned below.

"fields_group": [{
    "index": 1,
    "value": "test"
}, {
    "index": 2,
    "value": "test"
}, {
    "index": 3,
    "value": "test"
}, {
    "index": 4,
    "value": "test"
}, {
    "index": 5,
    "value": "test"
}]

Validations: 1) Index value should not be duplicate 2) Should allow indexes 1 to 5 only. 3) Make sure index exist for each value.

Can someone help me with Javascript that does the above in an optimal way? I tried with 2 for loops which is O(n²), but I need a faster solution.

Answer 1

You can use every() and add object as optional parameter to check for duplicate index values.

var obj = {"fields_group":[{"index":1,"value":"test"},{"index":2,"value":"test"},{"index":3,"value":"test"},{"index":4,"value":"test"},{"index":5,"value":"test"}]}

var result = obj.fields_group.every(function(e) {	
  if(!this[e.index] && e.index <= 5 && e.index > 0 && e.index) {
    this[e.index] = true;
    return true;
  }
}, {});

console.log(result)

You can also use regular expression /^[1-5]$/ to check index values.

var obj = {"fields_group":[{"index":1,"value":"test"},{"index":2,"value":"test"},{"index":3,"value":"test"},{"index":4,"value":"test"},{"index":5,"value":"test"}]}

var result = obj.fields_group.every(function(e) {	
  if(!this[e.index] && /^[1-5]$/.exec(e.index)) {
    this[e.index] = true;
    return true;
  }
}, {});

console.log(result)

Answer 2

Use the following approach with Array.map, Array.some and RegExp.test functions :

var obj = {"fields_group":[{"index":1,"value":"test"},{"index":2,"value":"test"},{"index":3,"value":"test"},{"index":4,"value":"test"},{"index":5,"value":"test"}]}
var isValid = function(obj){
    var indexes = obj.map(function(v){ return v.index; });
    return !indexes.some(function(v, k, a){ return a.lastIndexOf(v) !== k; }) 
            && indexes.length === indexes.map(Boolean).length 
            && /^[1-5]+$/.test(indexes.join(""));
}

console.log(isValid(obj.fields_group));  // true

• !indexes.some(function(v, k, a){ return a.lastIndexOf(v) !== k; }) - ensures that all indexes are unique
• indexes.length === indexes.map(Boolean).length - ensures that each index value exists(not empty)
• /^[1-5]+$/.test(indexes.join("") - ensures that there's should be indexes in range from 1 to 5 only

Answer 3

Another method:

function validate(fields_group) {
  if (fields_group.length > 5) {
    console.log("The array has more than 5 elements. The max is 5.");
    return false;
  }

  var idxs = {};
  for (var i = 0; i < fields_group.length; i++) {
    var obj = fields_group[i];
    if (obj.index == null || idxs[obj.index] || obj.index < 1 || obj.index > 5) {
      console.log("An object does not have a valid index.");
      return false;
    } else {
      idxs[obj.index] = true;
    }
  }
  console.log("The feilds group is valid.");
  return true;
}

I have measured the execution time (using performace.now() on Chrome) for the answers listed, and found this to be the fastest.