I would like to loop through an array and get the key and value of it. This is what I'm doing, but I don't get any output. What am I doing wrong?
let regexes = [];
regexes['some.thing'] = /([^.]+)[.\s]*/g;
_.each(regexes, function(regex, key) {
console.log(regex, key);
});
You are using array and adding a property to it which is not valid .Use object for it
let regexes = {};
regexes['some.thing'] = /([^.]+)[.\s]*/g;
_.each(regexes, function(regex, key) {
console.log(regex, key);
});
_.each iterates through the indices of the array. You are adding a non-numeric property to the array object. Your array is empty and _.each callback is not executed. It seems you want to use a regular object ({}) and not an array:
let regexes = {};
Now _.each should iterate through the object own (by using hasOwnProperty method) properties.
You are assigning a property to the array. Lodash is attempting to iterate through the numeric indices of the array, but there are none. Change the array to an object and Lodash will iterate through its enumerable properties:
let regexes = {};
regexes['some.thing'] = /([^.]+)[.\s]*/g;
_.forEach(regexes, function(regex, key) {
console.log(regex, key);
});
Alternatively, if using an array is necessary, simply push the value onto it:
let regexes = [];
regexes.push(/([^.]+)[.\s]*/g);
_.forEach(regexes, function(regex, i) {
console.log(regex, i);
});
Related
For Example :
I have an object and in that object, I have values in the array. I want to return the array which contains the key which contains the value passing as a variable.
function getValues(val , object){
return []; // return [b,c] because xyz are present in both
}
var object = {
"a" : ["abc", "cde","efg"],
"b" : ["asdf","asee","xyz"],
"c" : ["asaw","wewe","xyz"]
getValues("xyz", object);
}```
There are various ways to approach this.
One could be using Object's native functions:
function getValues(str, obj) {
return Object
// returns the entries pairs in a array of [key, value]
.entries(obj)
// from the array it searches the value for the string inputted and maps it back
.map(([key, array]) => array.includes(str) ? key : undefined)
// simply remove the undefined returned values from map()
.filter((value) => value);
};
This could have been done with reduce() as well but I found it easier to explain this way.
Another approach is using a for loop to iterate over the keys of the object:
function getValues(str, obj) {
let arr = [];
// Iterates through the object selecting its keys
for (let key in obj) {
// If the array of the current key has the string in it, includes in the array
if (obj[key].includes(str)) {
arr.push(key)
}
}
return arr;
}
I have an array object where there are key value pairs. I am trying to get the keys in that array using a loop but I am getting only 0. What is the problem with my code.
var strj = '{"name":"John","age":"30","cars":
[ {"type":"car", "year":"1998"},
{"type":"van", "year":"1995"}]}';
var myobj = JSON.parse(strj)
var care = myobj.cars.filter(c => c.type=='car');
Value of care
0:{type: "car", year: "1998"}
length:1
__proto__:Array(0)
Loop
for (var key in care){
if(care.hasOwnProperty(key)){
console.log(key)
}
}
care is a array type so you cannot do for (var key in care). You need to do for (var key in care[0]). This is because for (var key in care) will look for the key value in care and since it is a array it will always take 0 as a value in key(as you have only one object in array and its index is 0). That is why you got 0 in console.log.
var care =[{type: "car", year: "1998"}];
for (var key in care[0]){
if(care[0].hasOwnProperty(key)){
console.log(key)
}
}
care.forEach( ( singleCar ) => {
for ( var key in singleCar ){
console.log(key);
if( care.hasOwnProperty( key ) ){
console.log(key);
}
}
})
forEach will give you all the objects one by one. so you can check them.
As others have solved the issue, might i make a suggestion - Object.keys () gives an array of the keys for a given object. Since you are getting your filtered object and simply want its keys - the following will achieve that. Note that this is only using the code after you have filtered the original and have gained the "care" object.
As an aside, note that object.values() will give you an array of the values in a given object and object.entries() will give you arrays of the key / value pairing.
var care = {type: "car", year: "1998"};
var keys = Object.keys(care)
console.log(keys) // gives ["type","year"]
filter() method returns a Array of matches.
var care = myobj.cars.filter(c => c.type=='car'); // So, this returns an array.
care.forEach(element => {
console.log(Object.keys(element)); //Prints keys of each element
});
Well actually there is no problem in your code at all. But you just misunderstood the use of javascript filter. Javascript filter() creates new array that's why you are getting 0 as key. If you want to get only one matching element then find() is what you should use.
var strj = '{"name":"John","age":"30","cars":[{"type":"car", "year":"1998"},{"type":"van", "year":"1995"}]}';
var myobj = JSON.parse(strj)
var care = myobj.cars.filter(c => c.type == 'car'); // returns array
var care = myobj.cars.find(c => c.type == 'car'); // returns first matching object
var care = myobj.cars.findIndex(c => c.type == 'car'); // returns first matching index
Javascript filter() method => Read Here
Javascript find() => Read Here
Javascript findIndex() method => Read Here
Can we convert an Object to a 2D Array,
My Object is like this
So That Array Key will be like 'STARS_2' and value is ["STARS_4", "STARS_0", "STARS_12"]
with My attempts I can get something like this,
With this Code,
var testArray =[];
_.map(childFieldNames, function (value, key) {
var newArray = new Array();
newArray[key] = value;
testArray.push(newArray);
});
Here Keys are actually another array, which I do not want. I want key should be like 'STARS_2' , i.e. property of master object.
Is this what you need?
var ary2D = Object.keys(childFieldNames).map(function (key) {
return childFieldNames[key];
});
better version for what Shilly showed would be:
const arr2D = Object.values(childFieldNames);
Object.entries(obj)
E.g.
const objVariable = {name: "Ted", job: "Dentist"}
const 2dArray = Object.entries(objVariable)
console.log(2dArray) // will print [["name", "Ted"], ["job", "Dentist"]]
Object.entries is a static method that belongs to the Object class. As a parameter, it accepts an object and returns a two-dimensional array.
Read more about it here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries
You don’t need to create your structure into 2D array to just iterate over each key and its respective value(which is an array). If you want to iterate over it you can do something like this.
const object = {
a: [1,2,3],
b: [2,3,5]
};
for (const [key, value] of Object.entries(object)) {
value.forEach(v=>{
console.log(`${key}: ${v}`);
})
}
Why is my for for-each loop not iterating over my JavaScript associative array object?
// Defining an array
var array = [];
// Assigning values to corresponding keys
array["Main"] = "Main page";
array["Guide"] = "Guide page";
array["Articles"] = "Articles page";
array["Forum"] = "Forum board";
// Expected: loop over every item,
// yet it logs only "last" assigned value - "Forum"
for (var i = 0; i < array.length; i++) {
console.log(array[i]);
}
jQuery each() could be helpful: https://api.jquery.com/jQuery.each/
The .length property only tracks properties with numeric indexes (keys). You're using strings for keys.
You can do this:
var arr_jq_TabContents = {}; // no need for an array
arr_jq_TabContents["Main"] = jq_TabContents_Main;
arr_jq_TabContents["Guide"] = jq_TabContents_Guide;
arr_jq_TabContents["Articles"] = jq_TabContents_Articles;
arr_jq_TabContents["Forum"] = jq_TabContents_Forum;
for (var key in arr_jq_TabContents) {
console.log(arr_jq_TabContents[key]);
}
To be safe, it's a good idea in loops like that to make sure that none of the properties are unexpected results of inheritance:
for (var key in arr_jq_TabContents) {
if (arr_jq_TabContents.hasOwnProperty(key))
console.log(arr_jq_TabContents[key]);
}
edit — it's probably a good idea now to note that the Object.keys() function is available on modern browsers and in Node etc. That function returns the "own" keys of an object, as an array:
Object.keys(arr_jq_TabContents).forEach(function(key, index) {
console.log(this[key]);
}, arr_jq_TabContents);
The callback function passed to .forEach() is called with each key and the key's index in the array returned by Object.keys(). It's also passed the array through which the function is iterating, but that array is not really useful to us; we need the original object. That can be accessed directly by name, but (in my opinion) it's a little nicer to pass it explicitly, which is done by passing a second argument to .forEach() — the original object — which will be bound as this inside the callback. (Just saw that this was noted in a comment below.)
This is very simple approach. The advantage is you can get keys as well:
for (var key in array) {
var value = array[key];
console.log(key, value);
}
For ES6:
array.forEach(value => {
console.log(value)
})
For ES6 (if you want the value, index and the array itself):
array.forEach((value, index, self) => {
console.log(value, index, self)
})
If Node.js or the browser support Object.entries(), it can be used as an alternative to using Object.keys() (Pointy's answer).
const h = {
a: 1,
b: 2
};
Object.entries(h).forEach(([key, value]) => console.log(value));
// logs 1, 2
In this example, forEach uses destructuring assignment of an array.
There are some straightforward examples already, but I notice from how you've worded your question that you probably come from a PHP background, and you're expecting JavaScript to work the same way -- it does not. A PHP array is very different from a JavaScript Array.
In PHP, an associative array can do most of what a numerically-indexed array can (the array_* functions work, you can count() it, etc.). You simply create an array and start assigning to string indexes instead of numeric.
In JavaScript, everything is an object (except for primitives: string, numeric, boolean), and arrays are a certain implementation that lets you have numeric indexes. Anything pushed to an array will affect its length, and can be iterated over using Array methods (map, forEach, reduce, filter, find, etc.) However, because everything is an object, you're always free to simply assign properties, because that's something you do to any object. Square-bracket notation is simply another way to access a property, so in your case:
array['Main'] = 'Main Page';
is actually equivalent to:
array.Main = 'Main Page';
From your description, my guess is that you want an 'associative array', but for JavaScript, this is a simple case of using an object as a hashmap. Also, I know it's an example, but avoid non-meaningful names that only describe the variable type (e.g. array), and name based on what it should contain (e.g. pages). Simple objects don't have many good direct ways to iterate, so often we'll turn then into arrays first using Object methods (Object.keys in this case -- there's also entries and values being added to some browsers right now) which we can loop.
// Assigning values to corresponding keys
const pages = {
Main: 'Main page',
Guide: 'Guide page',
Articles: 'Articles page',
Forum: 'Forum board',
};
Object.keys(pages).forEach((page) => console.log(page));
arr_jq_TabContents[key] sees the array as an 0-index form.
Here is a simple way to use an associative array as a generic Object type:
Object.prototype.forEach = function(cb){
if(this instanceof Array) return this.forEach(cb);
let self = this;
Object.getOwnPropertyNames(this).forEach(
(k)=>{ cb.call(self, self[k], k); }
);
};
Object({a:1,b:2,c:3}).forEach((value, key)=>{
console.log(`key/value pair: ${key}/${value}`);
});
This is (essentially) incorrect in most cases:
var array = [];
array["Main"] = "Main page";
That creates a non-element property on the array with the name Main. Although arrays are objects, normally you don't want to create non-element properties on them.
If you want to index into array by those names, typically you'd use a Map or a plain object, not an array.
With a Map (ES2015+), which I'll call map because I'm creative:
let map = new Map();
map.set("Main", "Main page");
you then iterate it using the iterators from its values, keys, or entries methods, for instance:
for (const value of map.values()) {
// Here, `value` will be `"Main page"`, etc.
}
Using a plain object, which I'll creatively call obj:
let obj = Object.create(null); // Creates an object with no prototype
obj.Main = "Main page"; // Or: `obj["Main"] = "Main page";`
you'd then iterate its contents using Object.keys, Object.values, or Object.entries, for instance:
for (const value of Object.values(proches_X)) {
// Here, `value` will be `"Main page"`, etc.
}
var obj = {
no: ["no", 32],
nt: ["no", 32],
nf: ["no", 32, 90]
};
count = -1; // Which must be a static value
for (i in obj) {
count++;
if (obj.hasOwnProperty(i)) {
console.log(obj[i][count])
};
};
In this code I used the brackets method for call values in an array because it contained an array. However, briefly the idea which a variable i has a key of property and with a loop called both values of the associative array.
It is the perfect method.
You can do this:
var array = [];
// Assigning values to corresponding keys
array[0] = "Main page";
array[1] = "Guide page";
array[2] = "Articles page";
array[3] = "Forum board";
array.forEach(value => {
console.log(value)
})
It seems like almost every answer is not what was asked at the very first place.
It's seems bit off that foreach-loop does not work. and simple for-loop will not work as well because length property will be zero in case of associative arrays(one of the fallback). but for-in do the thing for associative array
// Defining an array
var array = [];
// Assigning values to corresponding keys
array["Main"] = "Main page";
array["Guide"] = "Guide page";
array["Articles"] = "Articles page";
array["Forum"] = "Forum board";
// Expected: loop over every item,
// yet it logs only "last" assigned value - "Forum"
for (var index in array) {
console.log(index,array[index]);
}
I have Hash obj:
var obj = {a,b,c,...};
obj = $H(obj);
I need to convert it to simple array
[a,b,c,..]
How can I do?
Thx.
Object.getValues(myObject) to get an Array of all values.
Object.getKeys(myObject) to get an Array of keys.
For 1.2 simply, Hash provides the same methods.
And don't use Objects {} to store lists like in your example. Arrays are for lists, Objects are for associative arrays.
EDIT:
Since version 1.3 Object.getValues and Object.getKeys has been deprecated and replaced by Object.keys resp Object.values.
since you use $H I am assuming older ver of mootools, 1.2.x since it got deprecated in 1.3 in favour of the new Object. construct
The hash had a .each method:
var Hobj = $H({
tool: "bar",
ghost: "goblin"
});
var arr = [];
Hobj.each(function(value, key) {
arr.push(value); // what to do with key?
});
console.log(arr);
an alternative that grabs the complete objects with their keys but not as array keys:
Hobj.each(function(value, key) {
var obj = {};
obj[key] = value;
arr.push(obj);
});
Assuming you want the values in the array:
var arr = [];
for(var prop in obj){
if(obj.hasOwnProperty(prop)){
arr.push(obj[prop]);
}
}
If you want the property names to be in the array:
var arr = [];
for(var prop in obj){
if(obj.hasOwnProperty(prop)){
arr.push(prop);
}
}
the hasOwnProperty call is important because it will filter out inherited functions and private members of the mooTools hash class that you don't probably want in your resulting array