How to access sub-values of a multi-dimensional object [duplicate] - javascript

This question already has answers here:
Convert a JavaScript string in dot notation into an object reference
(34 answers)
Closed 7 years ago.
is it possible to get a reference to an object with the object itself
obj
and the attributes in string form
'address.town.street'
so that at the end it resolves
obj.address.town.street
i could immageine smth like the eval() function.

Try
function getValue(obj, path) {
return path.split(".").reduce(function(obj, name){ return obj[name]}, obj);
}

Do not use eval. Use this instead
Object.prototype.nestedByString=function(reference){
var current=this;
path=reference.split(".");
for(var i=0;i<path.length;i++){
current=current[path[i]];
}
return current;
}
Here is a demo
I suppose that if you're allergic to extending native prototypes, you can do this
function nestedByString(obj,reference){
var current=obj;
path=reference.split(".");
for(var i=0;i<path.length;i++){
current=current[path[i]];
}
return current;
}

Related

Adding a key from a variable string (es6) when using spread syntax [duplicate]

This question already has answers here:
How to use a variable for a key in a JavaScript object literal?
(16 answers)
Closed 6 years ago.
I would like to know if there is a clean way to set the value of a key from a string variable when using spread syntax in es6?
Something like the following:
let keyVar = 'newKey'
let newObject = {keyVar:{some:'json'},...oldObject}
But this leads to:
{"keyVar":{"some":"json"}, ... }
rather than:
{"newKey":{"some":"json"}, ... }
You can use computed properties:
const keyVar = 'newKey';
const newObject = { [keyVar]: { some: 'json' } };
console.log(newObject);

Short for of creating an object from 2 variables [duplicate]

This question already has answers here:
How to use a variable for a key in a JavaScript object literal?
(16 answers)
Closed 6 years ago.
Is there a short form of doing such operation:
function doObject(key, value){
let object = {};
return object[key] = value;
}
UPD: forget about function, I use it just to isolate scope and provide to params key and value. I don't need to implement the function but logic that it does
const doObject = (key, value) => ({[key]: value});
// ^^^^^^^^^^^^ ^ ^^^^^
// 1 2 3
Arrow function syntax
Wrapping with braces allows you to return an object literal without the extended syntax. (Otherwise, it thinks the {} are the block delimiters.
Computed object literal property key.
You can use a computed property name for the object:
function doObject(key, value){
return {
[key]: value
};
}

Difference between object.prop and object["prop"] [duplicate]

This question already has answers here:
Accessing Properties in object [duplicate]
(3 answers)
Closed 7 years ago.
I used to believe that there is no difference between them but after seeing this piece of code, all my information about objects in Javascript failed.
var search = function(name) {
for(var x in friends) {
if(friends[x].firstName === name) {
console.log(friends[x]);
return friends[x];
}
}
};
This code works. But
var search = function(name) {
for(var x in friends) {
if(friends.x.firstName === name) {
console.log(friends.x);
return friends.x;
}
}
};
this doesn't.
Thanks for explaining.
friends.x is not the same thing as friends[x], it's the same thing as friends['x'].
When you use friends[x] the value x can be a variable (or any expression), but when you use friends.x the x is a literal name, it won't use the variable x.
As #Guffa already explained, friends.x and friends['x'] are the same, the difference in those approaches is that when you use [] this syntax you can use variables, 'property like this', or reserved words, this is good when you do not know exactly the property you will need.

jQuery expression as object key [duplicate]

This question already has answers here:
How to create an object property from a variable value in JavaScript? [duplicate]
(9 answers)
Accessing an object property with a dynamically-computed name
(19 answers)
Closed 8 years ago.
I need to figure out how to create a dynamic key string for an object. This expression makes JavaScript complain.
return {$(this).val(): true}; // returns an object e.g. {2: true}
What am I doing wrong?
You have to create the object, then use bracket notation for the dynamic key
var obj = {};
var val = $(this).val();
obj[val] = true;
return obj;
or a completely unnecessary one-liner
return (function(o,e) {o[e.value]=true; return o;})({}, this);
The JavaScript object literal syntax {x: y} specifies that x will be a (possibly) quoteless string, and y any value. You can't use this syntax for dynamic keys.
Use this instead:
var foo = {};
foo[$(this).val()] = true;
return foo;

Javascript variable object keys [duplicate]

This question already has answers here:
How to use a variable for a key in a JavaScript object literal?
(16 answers)
Closed 8 years ago.
I am attempting to add a variable key, with no luck.
Here's what I got so far:
mysql('translations',{
check: 'element_id',
element_id: element_id,
{'lang-'+lang_id}: value
});
The variable key is the last line of the function.
Any ideas?
You can't use expressions for the identifiers in an object literal.
First create the object, then you can use dynamic names:
var obj = {
check: 'element_id',
element_id: element_id,
}
obj['lang-'+lang_id] = value;
mysql('translations', obj);
You can do this:
var x = {
check: 'element_id',
element_id: element_id
};
x['lang-'+lang_id] = value;
mysql('translations', x);

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