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Get previous object item in javascript

I have an object with keys and data. From a key I want to get the previous item.
I've seen similar topics before but the solutions are really complicated.
I also added a function that does not work but how I wish it would work
Simplified code
let obj = {
slug: 'my-page',
title: 'My title',
description: 'My description',
content: 'My content'
};
let previous = obj.previousItem('description'); // Does not work
console.log(previous);
Expected result
{ title: 'My title'
}
ES5 or even ES6 is fine
I prefer a simple solution to a complicated one, maybe without loops

I think somethink like this
Object.prototype.previousItem = function(propName) {
const arr = Object.keys(this);
let indx = arr.indexOf(propName)-1;
if (indx<0) return null;
const result = {};
result[arr[indx]] = this[arr[indx]];
return result;
}

Object used to be to have no order, but actually they have and I would not rely on this order.
But anyway, you could filter by the next key/value pair and get an object.
let obj = { slug: 'my-page', title: 'My title', description: 'My description', content: 'My content' },
previous = Object.fromEntries(Object
.entries(obj)
.filter((_, i, { [i + 1]: next = [] }) => next[0] === 'description')
);
console.log(previous);

Object.prototype.previousItem = function(propName) {
const arr = Object.keys(this);
let indx = arr.indexOf(propName)-1;
if (indx<0) return null;
const result = Object.create(null); // just clear output
result[arr[indx]] = this[arr[indx]];
return result;
}
let obj = {
slug: 'my-page',
title: 'My title',
description: 'My description',
content: 'My content'
};
let previous = obj.previousItem('description'); // work
console.log(previous);

You can try following to get the previous item
let object = {
slug: 'my-page',
title: 'My title',
description: 'My description',
content: 'My content'
}
let previous = previousItem(object, 'description');
console.log(previous);
function previousItem(object, str) {
let lastKey = "";
for (const key in object) {
if (object.hasOwnProperty(key)) {
if (key == str){
lastKey = lastKey || key;
let obj = { };
obj[lastKey] = object[lastKey];
return obj;
} else {
lastKey = key;
}
}
}
}

Recursively find keys on an object

I have a javascript object structured like this;
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
Given an array of keys ['brand', 'group', 'newGroup', 'newSubGroup'] I want to split the keys into found and missing keys. So for the structure above I should get back;
present = ['brand', 'group']
missing = ['newGroup', 'newSubGroup']
I'm using ES6 and have lodash available, but struggling to find a clean way to produce this.
This is not to just check existence, it's recursively find the keys and return those present and the remaining ones.

Here's a pretty sketchy way that works.
const find = (keys, obj) => {
const string = JSON.stringify(obj);
return keys.reduce(({ present, missing }, key) => {
const match = string.match(new RegExp(`"${key}":`));
if (match) {
present.push(key);
} else {
missing.push(key);
}
return { present, missing };
}, { present: [], missing: [] });
}

You can use this function made for you ;)
var getAttrs = function(obj) {
return [].concat.apply([], Object.keys(obj).map(function (key) {
var results = [key]
if (typeof obj[key] === 'object') {
Array.prototype.push.apply(results, getAttrs(obj[key]))
}
return results
}))
}
It return the list of properties and children properties.
getAttrs({brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}})
> ["brand", "group", "subGroup", "items", "otherSub", "items"]
And you can use it like so:
var lookingFor = ['brand', 'group', 'newGroup', 'newSubGroup']
var existings = getAttrs(obj)
var missings = []
var presents = []
lookingFor.forEach(attr => {
if (existings.indexOf(attr) === -1) {
missings.push(attr)
} else {
presents.push(attr)
}
})

I wrote a function to recursively get unique keys from a nested object, then filtered the array of all the keys you mentioned checking which were present in the result of my function.
var thisObject = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
};
var arr_full = ['brand', 'group', 'newGroup', 'newSubGroup'] ;
var key_array = [];
function addToKeyArray( key_array, object ){
for( var key in object ){
// only get unique keys
if( key_array.indexOf( key ) === -1 ){
key_array.push( key );
}
// concat the result of calling this function recurrsively on object[key]
key_array.concat( addToKeyArray( key_array, object[key] ) );
}
return key_array;
}
var test = addToKeyArray( [], thisObject );
var missing = arr_full.filter( function( el ) {
return test.indexOf( el ) < 0;
});
console.log( test );
console.log( missing )

You can create recursive function using for...in loop inside another function and return object as result..
var obj = {"brand":{"group":{"subGroup":{"items":[]},"otherSub":{"items":[]}}}}
var keys = ['brand', 'group', 'newGroup', 'newSubGroup'] ;
function findKeys(data, keys) {
keys = keys.slice();
function findPresent(data, keys) {
var result = []
for(var i in data) {
if(typeof data[i] == 'object') result.push(...findPresent(data[i], keys))
var index = keys.indexOf(i);
if(index != -1) result.push(...keys.splice(index, 1))
}
return result
}
return {present: findPresent(data, keys), missing: keys}
}
console.log(findKeys(obj, keys))

To keep things clean and readable you can use "for in", inside a nested function for your recursion.
function recur(obj) {
let preMiss = {
present: [],
missing: []
}
let root = traverse => {
for (let key in traverse) {
if (Array.isArray(traverse[key].items)) {
preMiss.missing.push(key);
}
if (typeof traverse[key] === 'object' && !Array.isArray(traverse[key].items)) {
preMiss.present.push(key);
root(traverse[key])
}
}
}
root(obj);
return preMiss;
}
const object = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
}
console.log(Object.entries(recur(object)));

var toFind = ['brand', 'group', 'newGroup', 'newSubGroup'],
found = [];
var o = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
}
//called with every property and its value
function process(key,value) {
var i = toFind.indexOf(key);
if(i !== -1){
found.push(key);
toFind.splice(i, 1);
}
}
function traverse(o,func) {
if(!toFind.length) return;
for (var i in o) {
func.apply(this,[i,o[i]]);
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
traverse(o[i],func);
}
}
}
traverse(o,process);
console.log(found); // present
console.log(toFind); // absent
Traverse method taken from https://stackoverflow.com/a/722732/1335165

Even though this question is a bit older, I want to present a rather short solution to the problem.
const recursivelyGetKeys = obj => Object.keys(obj).map(key => typeof obj[key] === 'object'
? [...recursivelyGetKeys(obj[key]), key] : [key]).reduce((p, c) => [...p, ...c], [])
This function will return all keys in the object, so a call to the array arr with
const arr = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
}
will output:
const keys = recursivelyGetKeys(arr) // = ["items", "subGroup", "items", "otherSub", "group", "brand"]
Now to find the intersection set of this and find = ['brand', 'group', 'newGroup', 'newSubGroup'], do:
const found = keys.filter(key => find.some(val === key))
const missing = keys.filter(key => find.every(val !== key))

Getting name of key with value null

I am running a loop through my array to check if calendar and tpoint have values. In my else statement of my if-statement I am attempting to get the key's name with var notSelected = (obj.prop.subProp).val() !== '';.
I know I am off with my method.. I am just unsure how to get the key name.
So, with my example, since the values in tpoint are empty, I am wanting the var notSelected to equal tpoint.
Anyone know how I can do this?
var packageContents = {
'packages': [
{
'price': '23',
'name': 'Bronze Bundle Package',
'calendar': {
'type': '2year',
'color': 'Brushed Nickel',
},
'tpoint': {
'type': '',
'touches': '',
'years': '',
}
}
]
};
var bundleSet = null;
var bundleSet = null;
packageContents.packages.forEach(function (obj) {
for (var prop in obj) {
if (prop === 'calendar' || prop === 'tpoint') {
for (var subProp in obj[prop]) {
if (obj[prop][subProp] !== '') {
bundleSet = true;
} else {
bundleSet = false;
var notSelected = (obj.prop.subProp).val() !== '';
console.log(notSelected);
}
}
}
}
console.log(bundleSet);
});

What about something like this:
function hasEmptyProps(prop) {
return Object.values(prop).some(x => x === '');
}
const result = packageContents.packages.map(x => {
if (hasEmptyProps(x.calendar)) {
return 'calendar';
} else if (hasEmptyProps(x.tpoint)) {
return 'tpoint'
} else {
return '';
}
})
console.log(result)
Would return ["tpoint"] (or an array of "calendar", "", or "tpoint")

check the existence of a key in associative arrays

Tell me, how correctly to check the existence of a key in associative arrays?
For example:
var mydata = {
key1: '',
key2: {
subkey1: {
subkey1_1: {
value1: ''
value2" '',
},
},
subkey2: '';
},
}
if ((mydata.key2 != undefined) && (mydata.key2.subkey1 != undefined) && (mydata.key2.subkey1.subkey1_1 != undefined))
mydata.key2.subkey1.subkey1_1.value1 = 'test';
Too long and confusing
((mydata.key2 != undefined) && (mydata.key2.subkey1 != undefined) && (mydata.key2.subkey1.subkey1_1 != undefined))
I would like to use a simpler function, like
safeSet(mydata.key2.subkey1.subkey1_1.value1, 'test');
or
if (is_undefined(mydata.key2.subkey1.subkey1_1.value1) == true)
mydata.key2.subkey1.subkey1_1.value1 = 'test'; // now - error if 'mydata.key2.subkey1.subkey1_1' not exist

You can create custom function using reduce() to test if nested property exists. You can just pass key as string.
var mydata = {
key1: '',
key2: {
subkey1: {
subkey1_1: {
value1: '',
value2: '',
},
},
subkey2: ''
},
}
function safeSet(key, data) {
return key.split('.').reduce(function(r, e) {
return r ? r[e] : undefined;
}, data) != undefined
}
console.log(safeSet('key2.subkey1.subkey1_1.value1', mydata))

You should use the in operator:
"key" in obj // true, regardless of the actual value
Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:
obj.hasOwnProperty("key") // true
hope this would help you.
Source: http://www.advancesharp.com/questions/628/checking-if-an-associative-array-key-exists-in-javascript

Alternatively, you can make use of the .has() method of Lodash.
Then, you would only need to check:
if (_.has(mydata, 'key2.subkey1.subkey1_1.value1')
mydata.key2.subkey1.subkey1_1.value1 = 'test';

For trying to get something in a nested structure I'd do something like this:
function getPath(element, path) {
var handledSoFar = [];
for (var i = 0; i < path.length; i++) {
var property = path[i];
handledSoFar.push(property);
if (typeof element[property] === 'undefined') {
throw new Error('Path ' + handledSoFar.join('->') + ' is undefined');
}
element = object[property];
}
return element;
}
var mydata = {
key1: '',
key2: {
subkey1: {
subkey1_1: {
value1: '',
value2: 'hi'
}
},
subkey2: ''
}
};
// Prints 'hi'
console.log(getPath(mydata, ['key2', 'subkey1', 'subkey1_1', 'value2']));
// Throws error 'Path key2->subkey2->subkey1_1 is undefined'
console.log(getPath(mydata, ['key2', 'subkey1', 'subkey1_1', 'value2']));
Of course keeping track of the search in handledSoFar is optional but might be useful for development / debugging.

You can also use the lodash deep field selector: lodash.get (documentation)
const get = require('lodash.get');
const set = require('lodash.set');
if (!get(mydata, 'key2.subkey1.subkey1_1.value1')) {
set(mydata, 'key2.subkey1.subkey1_1.value1', 'test');
}

You could split the path and make a check if the following element exist. If not assign an object to the new property.
Return then the value of the property.
At the end assign the value.
function setValue(object, path, value) {
var fullPath = path.split('.'),
way = fullPath.slice(),
last = way.pop();
way.reduce(function (r, a) {
return r[a] = r[a] || {};
}, object)[last] = value;
}
var object = { key1: '', key2: { subkey1: { subkey1_1: { value1: '', value2: '' } }, subkey2: '' } };
setValue(object, 'key2.subkey1.subkey1_1.value1', 'test');
console.log(object);

The problem with the example function that you proposed:
safeSet(mydata.key2.subkey1.subkey1_1.value1, 'test');
or
is_undefined(mydata.key2.subkey1.subkey1_1.value1)
Is that the mydata.key2.subkey1... part is run before the function is called. So if one of the subkeys does not exist, an exception will be thrown before your code is reached.
You could get something similar using a callback though...
safeSet(function(val) { mydata.key2.subkey1.subkey1_1.value1 = val; }, 'test')
the implementation of safeSet would then be:
var safeSet = function(setterFunc, val) {
try {
setterFunc(val);
} catch (e) {
if (e instanceof TypeError) {
return false;
} else {
throw e;
}
}
return true;
}
safeSet returns true if the value was set, and false otherwise.

javascript: Alter the output of a function to the specified decimal place

I am not very good with my javascript but recently needed to work with a library to output an aggregated table. Was using fin-hypergrid.
There was a part where I need to insert a sum function (rollups.sum(11) in this example)to an object so that it can compute an aggregated value in a table like so:
aggregates = {Value: rollups.sum(11)}
I would like to change this value to return 2 decimal places and tried:
rollups.sum(11).toFixed(2)
However, it gives the error : "rollups.sum(...).toFixed is not a function"
If I try something like:
parseFloat(rollups.sum(11)).toFixed(2)
it throws the error: "can't assign to properties of (new String("NaN")): not an object"
so it has to be a function object.
May I know if there is a way to alter the function rollups.sum(11) to return a function object with 2 decimal places?
(side info: rollups.sum(11) comes from a module which gives:
sum: function(columnIndex) {
return sum.bind(this, columnIndex);
}
)
Sorry I could not post sample output here due to data confidentiality issues.
However, here is the code from the example I follow. I basically need to change rollups.whatever to give decimal places. The "11" in sum(11) here refers to a "column index".
window.onload = function() {
var Hypergrid = fin.Hypergrid;
var drillDown = Hypergrid.drillDown;
var TreeView = Hypergrid.TreeView;
var GroupView = Hypergrid.GroupView;
var AggView = Hypergrid.AggregationsView;
// List of properties to show as checkboxes in this demo's "dashboard"
var toggleProps = [{
label: 'Grouping',
ctrls: [
{ name: 'treeview', checked: false, setter: toggleTreeview },
{ name: 'aggregates', checked: false, setter: toggleAggregates },
{ name: 'grouping', checked: false, setter: toggleGrouping}
]
}
];
function derivedPeopleSchema(columns) {
// create a hierarchical schema organized by alias
var factory = new Hypergrid.ColumnSchemaFactory(columns);
factory.organize(/^(one|two|three|four|five|six|seven|eight)/i, { key: 'alias' });
var columnSchema = factory.lookup('last_name');
if (columnSchema) {
columnSchema.defaultOp = 'IN';
}
//factory.lookup('birthState').opMenu = ['>', '<'];
return factory.schema;
}
var customSchema = [
{ name: 'last_name', type: 'number', opMenu: ['=', '<', '>'], opMustBeInMenu: true },
{ name: 'total_number_of_pets_owned', type: 'number' },
{ name: 'height', type: 'number' },
'birthDate',
'birthState',
'employed',
{ name: 'income', type: 'number' },
{ name: 'travel', type: 'number' }
];
var peopleSchema = customSchema; // or try setting to derivedPeopleSchema
var gridOptions = {
data: people1,
schema: peopleSchema,
margin: { bottom: '17px' }
},
grid = window.g = new Hypergrid('div#json-example', gridOptions),
behavior = window.b = grid.behavior,
dataModel = window.m = behavior.dataModel,
idx = behavior.columnEnum;
console.log('Fields:'); console.dir(behavior.dataModel.getFields());
console.log('Headers:'); console.dir(behavior.dataModel.getHeaders());
console.log('Indexes:'); console.dir(idx);
var treeView, dataset;
function setData(data, options) {
options = options || {};
if (data === people1 || data === people2) {
options.schema = peopleSchema;
}
dataset = data;
behavior.setData(data, options);
idx = behavior.columnEnum;
}
// Preset a default dialog options object. Used by call to toggleDialog('ColumnPicker') from features/ColumnPicker.js and by toggleDialog() defined herein.
grid.setDialogOptions({
//container: document.getElementById('dialog-container'),
settings: false
});
// add a column filter subexpression containing a single condition purely for demo purposes
if (false) { // eslint-disable-line no-constant-condition
grid.getGlobalFilter().columnFilters.add({
children: [{
column: 'total_number_of_pets_owned',
operator: '=',
operand: '3'
}],
type: 'columnFilter'
});
}
window.vent = false;
//functions for showing the grouping/rollup capabilities
var rollups = window.fin.Hypergrid.analytics.util.aggregations,
aggregates = {
totalPets: rollups.sum(2),
averagePets: rollups.avg(2),
maxPets: rollups.max(2),
minPets: rollups.min(2),
firstPet: rollups.first(2),
lastPet: rollups.last(2),
stdDevPets: rollups.stddev(2)
},
groups = [idx.BIRTH_STATE, idx.LAST_NAME, idx.FIRST_NAME];
var aggView, aggViewOn = false, doAggregates = false;
function toggleAggregates() {
if (!aggView){
aggView = new AggView(grid, {});
aggView.setPipeline({ includeSorter: true, includeFilter: true });
}
if (this.checked) {
grid.setAggregateGroups(aggregates, groups);
aggViewOn = true;
} else {
grid.setAggregateGroups([], []);
aggViewOn = false;
}
}
function toggleTreeview() {
if (this.checked) {
treeView = new TreeView(grid, { treeColumn: 'State' });
treeView.setPipeline({ includeSorter: true, includeFilter: true });
treeView.setRelation(true, true);
} else {
treeView.setRelation(false);
treeView = undefined;
delete dataModel.pipeline; // restore original (shared) pipeline
behavior.setData(); // reset with original pipeline
}
}
var groupView, groupViewOn = false;
function toggleGrouping(){
if (!groupView){
groupView = new GroupView(grid, {});
groupView.setPipeline({ includeSorter: true, includeFilter: true });
}
if (this.checked){
grid.setGroups(groups);
groupViewOn = true;
} else {
grid.setGroups([]);
groupViewOn = false;
}
}

you may try:
(rollups.sum(11)).toFixed(2)
enclosing number in parentheses seems to make browser bypass the limit that identifier cannot start immediately after numeric literal
edited #2:
//all formatting and rendering per cell can be overridden in here
dataModel.getCell = function(config, rendererName) {
if(aggViewOn)
{
if(config.columnName == "total_pets")
{
if(typeof(config.value) == 'number')
{
config.value = config.value.toFixed(2);
}
else if(config.value && config.value.length == 3 && typeof(config.value[1]) == 'number')
{
config.value = config.value[1].toFixed(2);
}
}
}
return grid.cellRenderers.get(rendererName);
};