在对象数组中搜索匹配的属性和值对

Question

I am trying to solve a freeCodeCamp exercise and have gotten stuck. The goal of the exercise is this: Make a function that looks through an array of objects (first argument) and returns an array of all objects that have matching property and value pairs (second argument). Each property and value pair of the source object has to be present in the object from the collection if it is to be included in the returned array.

So what I did, was to make an array of the key pairs of the collection, and another array with the key pairs of the source. The I nested for-loops in order to find matching keys, and if those keys are found, then compare the properties.

But somehow, my code returns no matches.

var collection = [{
  first: "Romeo",
  last: "Montague"
}, {
  first: "Mercutio",
  last: null
}, {
  first: "Tybalt",
  last: "Capulet"
}];
var source = {
  last: "Capulet"
};

var collectionKeys = [];
for (var i = 0; i < collection.length; i++) {
  collectionKeys.push(Object.keys(collection[i]));
}
var sourceKeys = Object.keys(source);

//for every key pair
for (var t = 0; t < collectionKeys.length; t++) {
  //for every key in key pair
  for (var x = 0; x < collectionKeys[t].length; x++) {
    //for every key in search
    for (var y = 0; y < sourceKeys.length; y++) {
      //see if a key matches
      if (sourceKeys[y] == collectionKeys[t][x]) {
        //see if the value matches
        if (collection[collectionKeys[t][x]] == source[sourceKeys[y]]) {
          console.log(collection[t]);
        } else {
          console.log("value not found");
        }
      } else {
        console.log("key not found");
      }
    }
  }
}

Can anybody point out what I'm doing wrong?

I've also created a JSfiddle if you want to tinker.

Answer 1

be more explicit in your declarations - helps to read the code easier:

var sourceKeys = Object.keys(source),
    i = 0, 
    j = 0,
    collectionLength = collection.length,
    sourceKeysLength = sourceKeys.length;

while (i < collectionLength) {
    j = 0;
    while (j < sourceKeysLength) {
        if (sourceKeys[j] in collection[i] && source[sourceKeys[j]] === collection[i][sourceKeys[j]]) {
            console.log('found one!');
        }
        j++;
    }
    i++;
}

https://jsfiddle.net/fullcrimp/1cyy8z64/

Answer 2

I was also stuck on this for a good hour, when I stumbled upon a couple resources to assist.

I found that rather than the mess of nested for loops, I could use the built in looping methods to greatly simplify my code.

here is where I found my explanation:

https://github.com/Rafase282/My-FreeCodeCamp-Code/wiki/Bonfire-Where-art-thou

function where(collection, source) {
  var arr = [];
  var keys = Object.keys(source);
  // Filter array and remove the ones that do not have the keys from source.
  arr = collection.filter(function(obj) {
    //Use the Array method every() instead of a for loop to check for every key from source.
    return keys.every(function(key) {
      // Check if the object has the property and the same value.
      return obj.hasOwnProperty(key) && obj[key] === source[key];
    });
  });

  return arr;
}

Answer 3

Some insight here with clear understanding and less loops.

some new javascript function like some, filter, map are really handy to make code tidier as well.

function whatIsInAName(collection, source) {
  // What's in a name?
  var arr = [];
  // Only change code below this line
  collection.some(function(obj){
      var sk = Object.keys(source); //keys of source object
      var sv = Object.values(source); //values of source object
      var temp = 0; 
      for(i=0;i<sk.length;i++){ // run until the number of source properties length is reached.
        if(obj.hasOwnProperty(sk[i]) && obj[sk[i]] === sv[i]){ // if it has the same properties and value as parent object from collection 
          temp++; //temp value is increased to track if it has matched all the properties in an object
        }
      }
      if(sk.length === temp){ //if the number of iteration has matched the temp value 
        arr.push(obj);
        temp = 0; // make temp zero so as to count for the another object from collection
      }
  })
  // Only change code above this line
  return arr;
}

Answer 4

 var collection = [{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }]; var source = { last: "Capulet" }; var collectionKeys = []; for (var i = 0; i < collection.length; i++) { collectionKeys.push(Object.keys(collection[i])); } var sourceKeys = Object.keys(source); //for every key pair for (var t = 0; t < collectionKeys.length; t++) { //for every key in key pair for (var x = 0; x < collectionKeys[t].length; x++) { //for every key in search for (var y = 0; y < sourceKeys.length; y++) { //see if a key matches if (sourceKeys[y] == collectionKeys[t][x]) { if (collection[t][collectionKeys[t][x]] == source[sourceKeys[y]]) { alert(collection[t].first+ " "+collection[t].last); } else { console.log("value not found"); } } else { console.log("key not found"); } } } }

Change collection[collectionKeys[t][x]] to collection[t][collectionKeys[t][x]].. collection[collectionKeys[t][x]] gives undefined in console.

Answer 5

This is what I came to on the same problem.

function whereAreYou(collection, source) {
  // What's in a name?

  // Only change code below this line

  var arr = [];
  var validObject;

// check each object
  for  (var each_object in collection ){
    validObject = true;
    for (var key in source ){
      if ( collection[each_object].hasOwnProperty(key)){
        if ( collection[each_object][key] != source[key]){ 
       // if no valid key
       validObject = false;
     } 
   } else {
    // if no valid value
     validObject = false;
   }
 }
  // otherwise, give it a green light
 if(validObject){
  arr.push(collection[each_object]);
  }   
}
return arr;

}

Answer 6

function whatIsInAName(collection, source) {
  const keyCount = Object.keys(source).length;
  return collection.filter((item) => {
    return Object.entries(item).reduce((acc, [key, value], _, arr) => {
      if (keyCount > arr.length) {
        acc = false;
      } else if (keyCount === arr.length && !source[key]) {
        acc = false;
      } else if (source[key] && source[key] !== value) {
        acc = false;
      }
      return acc;
    }, true)
  })
}