tips on transforming an array object and generating a fresh array

Question

tips on transforming an array object and generating a fresh array

Below is a JavaScript array that I have:

var names = [{name:"high",id:1},{name:"high",id:2}, 
{name:"low",id:1},  {name:"low",id:2},{name:"medium",id:1},{name:"medium",id:2}];

I am looking to transform this array into a new format like the one shown below.

var newArr=[{name:high,items:[1,2]},{name:low,items:[1,2]},{name:medium,items:[1,2]}];

If you have any suggestions on how to achieve this transformation, please let me know.

javascript arrays

Answer 1

Answer №1

Underscorejs Library Approach

var obj = {};

_.each(names, function (e) {
    var o = obj[e.name];
    if (o) {
        o.items.push(e.id);
    } else {
        o = {name: e.name, items: [e.id]};
    }
    obj[e.name] = o;
});

var result = _.map(obj, function (e) {return e;});

Pure JavaScript Methodology

var obj = {};
for (var i = 0; i < names.length; i++) {
    var e = names[i];
    var o = obj[e.name];
    if (o) {
        o.items.push(e.id);
    } else {
        o = {name: e.name, items: [e.id]};
    }
    obj[e.name] = o;
}
var result = [];
for (var k in obj) {
    if (obj.hasOwnProperty(k)) {
        result.push(obj[k]);
    }
};

Answer 2

Underscorejs Library Approach

var obj = {};

_.each(names, function (e) {
    var o = obj[e.name];
    if (o) {
        o.items.push(e.id);
    } else {
        o = {name: e.name, items: [e.id]};
    }
    obj[e.name] = o;
});

var result = _.map(obj, function (e) {return e;});

Pure JavaScript Methodology

var obj = {};
for (var i = 0; i < names.length; i++) {
    var e = names[i];
    var o = obj[e.name];
    if (o) {
        o.items.push(e.id);
    } else {
        o = {name: e.name, items: [e.id]};
    }
    obj[e.name] = o;
}
var result = [];
for (var k in obj) {
    if (obj.hasOwnProperty(k)) {
        result.push(obj[k]);
    }
};

Answer 3

Answer №2

Presenting a straightforward solution without the need for any external libraries.

var uniqueNames = []
for ( var key in names ) {
    var found = findItemInArray(names[key].name,uniqueNames);
    if(found) {                // Another entry with the same name is already in uniqueNames
       var itemsList = found.items.push(names[key].id);    // Add the id to the existing item's list of items
    } else {                   // No other entry with the same name exists in uniqueNames
       var newEntry = {name:names[key].name, items:names[key].id};
       uniqueNames.push(newEntry);
    }
}

I also created this handy function that checks if an item already exists in uniqueNames

function findItemInArray(name,array){
    for(var index in array){
       if(array[index].name === name){
           return array[index];
       }
    return null;
}

Answer 4

Presenting a straightforward solution without the need for any external libraries.

var uniqueNames = []
for ( var key in names ) {
    var found = findItemInArray(names[key].name,uniqueNames);
    if(found) {                // Another entry with the same name is already in uniqueNames
       var itemsList = found.items.push(names[key].id);    // Add the id to the existing item's list of items
    } else {                   // No other entry with the same name exists in uniqueNames
       var newEntry = {name:names[key].name, items:names[key].id};
       uniqueNames.push(newEntry);
    }
}

I also created this handy function that checks if an item already exists in uniqueNames

function findItemInArray(name,array){
    for(var index in array){
       if(array[index].name === name){
           return array[index];
       }
    return null;
}

Answer 5

Answer №3

Presented below is a solution that does not rely on external libraries:

/**
 * Function to add an object to a set.
 *
 * @param {object} theSet The set where the object will be added.
 * @param {object} theObject The object to be added.
 *
 * @return {object} theSet with theObject added.
 *
 * @note Assumes that theObject.name is the key,
 *       and theObject.id should be in the value array.
 * @note This operates as a callback for Array.prototype.reduce().
 */
function collect(theSet, theObject) {
    if (theSet.hasOwnProperty(theObject.name)) {
        theSet[theObject.name].push(theObject.id);
    } else {
        theSet[theObject.name] = [theObject.id];
    }
    return theSet;
}
var names = [{name:"high",id:5},{name:"high",id:6}, 
             {name:"low",id:1},  {name:"low",id:2},{name:"medium",id:3},{name:"medium",id:4}],
    combinedSet = names.reduce(collect, {}), // Step 1
    final = [],
    key;

// Step 2
for (key in combinedSet) {
    if (combinedSet.hasOwnProperty(key)) {
        final.push(
            {
                "name" : key,
                "items": combinedSet[key]
            }
        );
    }
}

The initial step involves organizing the IDs under their respective object names. This is achieved using Array.prototype.reduce with the callback function collect. The outcome of this process is stored in the combinedSet variable.

In the subsequent step, we convert the set created in Step 1 into the final array, creating objects wherein the keys from the set are assigned to the name attribute and the values are assigned to the items attribute. Since reduce cannot be used here as before, a basic for loop is employed. It's worth noting the inclusion of hasOwnProperty check to mitigate potential issues arising from modifications made to Object.prototype; without this safeguard, unintended items could appear in the set, leading to errors.

Answer 6

Presented below is a solution that does not rely on external libraries:

/**
 * Function to add an object to a set.
 *
 * @param {object} theSet The set where the object will be added.
 * @param {object} theObject The object to be added.
 *
 * @return {object} theSet with theObject added.
 *
 * @note Assumes that theObject.name is the key,
 *       and theObject.id should be in the value array.
 * @note This operates as a callback for Array.prototype.reduce().
 */
function collect(theSet, theObject) {
    if (theSet.hasOwnProperty(theObject.name)) {
        theSet[theObject.name].push(theObject.id);
    } else {
        theSet[theObject.name] = [theObject.id];
    }
    return theSet;
}
var names = [{name:"high",id:5},{name:"high",id:6}, 
             {name:"low",id:1},  {name:"low",id:2},{name:"medium",id:3},{name:"medium",id:4}],
    combinedSet = names.reduce(collect, {}), // Step 1
    final = [],
    key;

// Step 2
for (key in combinedSet) {
    if (combinedSet.hasOwnProperty(key)) {
        final.push(
            {
                "name" : key,
                "items": combinedSet[key]
            }
        );
    }
}

The initial step involves organizing the IDs under their respective object names. This is achieved using Array.prototype.reduce with the callback function collect. The outcome of this process is stored in the combinedSet variable.

In the subsequent step, we convert the set created in Step 1 into the final array, creating objects wherein the keys from the set are assigned to the name attribute and the values are assigned to the items attribute. Since reduce cannot be used here as before, a basic for loop is employed. It's worth noting the inclusion of hasOwnProperty check to mitigate potential issues arising from modifications made to Object.prototype; without this safeguard, unintended items could appear in the set, leading to errors.

Answer 7

Answer №4

If you need a function to group items, consider using underscoreJs groupBy:

Check out this example on jsFiddle

var names = [{name:"high",id:1},{name:"high",id:2}, {name:"low",id:1},  {name:"low",id:2},{name:"medium",id:1},{name:"medium",id:2}];

console.debug(_.groupBy(names, 'name'));
// This will return an object with grouped arrays based on the 'name' key

Answer 8

If you need a function to group items, consider using underscoreJs groupBy:

Check out this example on jsFiddle

var names = [{name:"high",id:1},{name:"high",id:2}, {name:"low",id:1},  {name:"low",id:2},{name:"medium",id:1},{name:"medium",id:2}];

console.debug(_.groupBy(names, 'name'));
// This will return an object with grouped arrays based on the 'name' key

tips on transforming an array object and generating a fresh array

Answer №1

Underscorejs Library Approach

Pure JavaScript Methodology

Answer №2

Answer №3

Answer №4

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