This question already has answers here:
How to set value to a property in a Javascript object, which is identified by an array of keys
(2 answers)
Closed 3 years ago.
I have an object that resembles this:
const obj = {
prop1: {
prop2: {
value: 'something',
...otherProps
}
},
...otherProps
}
And an array that looks like this:
const history = ['prop1', 'prop2', 'value']
How do I assign the property value of prop2 a new value in a way that would also work for any other depth.
Just loop through the property list and get each property of the object.
const obj = {
prop1: {
prop2: {
value: 'something'
}
}
};
const history = ['prop1', 'prop2', 'value'];
console.log(setPropertyValue(obj, history, "test"));
console.log(getPropertyValue(obj, history));
function getPropertyValueContainer(values, propertyList) {
var copy = propertyList.slice(), propertyName = copy.pop();
for (var property of copy) values = values[property];
return { propertyName: propertyName, values: values };
}
function getPropertyValue(values, propertyList) {
var container = getPropertyValueContainer(values, propertyList);
return container.values[container.propertyName];
}
function setPropertyValue(values, propertyList, value) {
var container = getPropertyValueContainer(values, propertyList);
return container.values[container.propertyName] = value;
}
You can use references.
So here i am taking reference of object in a variable untill i key equal to value and than adding value using that ref.
const obj = { prop1: { prop2: { value: 'something'}}}
const history = ['prop1', 'prop2', 'value']
let ref = obj;
history.forEach((e,index)=>{
if(e !== 'value' ) ref = ref[e]
})
ref.value = 'xyz'
console.log(obj)
For example if I have two objects:
var foo = {
x: "bar",
y: "baz"
}
and
var oof = {}
and I wanted to transfer the x and y values from foo to oof. Is there a way to do that using the es6 destructuring syntax?
perhaps something like:
oof{x,y} = foo
While ugly and a bit repetitive, you can do
({x: oof.x, y: oof.y} = foo);
which will read the two values of the foo object, and write them to their respective locations on the oof object.
Personally I'd still rather read
oof.x = foo.x;
oof.y = foo.y;
or
['x', 'y'].forEach(prop => oof[prop] = foo[prop]);
though.
IMO this is the easiest way to accomplish what you're looking for:
let { prop1, prop2, prop3 } = someObject;
let data = { prop1, prop2, prop3 };
// data === { prop1: someObject.prop1, ... }
Basically, destructure into variables and then use the initializer shorthand to make a new object. No need for Object.assign
I think this is the most readable way, anyways. You can hereby select the exact props out of someObject that you want. If you have an existing object you just want to merge the props into, do something like this:
let { prop1, prop2, prop3 } = someObject;
let data = Object.assign(otherObject, { prop1, prop2, prop3 });
// Makes a new copy, or...
Object.assign(otherObject, { prop1, prop2, prop3 });
// Merges into otherObject
Another, arguably cleaner, way to write it is:
let { prop1, prop2, prop3 } = someObject;
let newObject = { prop1, prop2, prop3 };
// Merges your selected props into otherObject
Object.assign(otherObject, newObject);
I use this for POST requests a lot where I only need a few pieces of discrete data. But, I agree there should be a one liner for doing this.
EDIT: P.S. -
I recently learned you can use ultra destructuring in the first step to pull nested values out of complex objects! For instance...
let { prop1,
prop2: { somethingDeeper },
prop3: {
nested1: {
nested2
}
} = someObject;
let data = { prop1, somethingDeeper, nested2 };
Plus, you could use spread operator instead of Object.assign when making a new object:
const { prop1, prop2, prop3 } = someObject;
let finalObject = {...otherObject, prop1, prop2, prop3 };
Or...
const { prop1, prop2, prop3 } = someObject;
const intermediateObject = { prop1, prop2, prop3 };
const finalObject = {...otherObject, ...intermediateObject };
No, destructuring does not support member expressions in shorthands but only plain propertynames at the current time. There have been talks about such on esdiscuss, but no proposals will make it into ES6.
You might be able to use Object.assign however - if you don't need all own properties, you still can do
var foo = …,
oof = {};
{
let {x, y} = foo;
Object.assign(oof, {x, y})
}
Other than Object.assign there is the object spread syntax which is a Stage 2 proposal for ECMAScript.
var foo = {
x: "bar",
y: "baz"
}
var oof = { z: "z" }
oof = {...oof, ...foo }
console.log(oof)
/* result
{
"x": "bar",
"y": "baz",
"z": "z"
}
*/
But to use this feature you need to use stage-2 or transform-object-rest-spread plugin for babel. Here is a demo on babel with stage-2
BabelJS plugin
If you are using BabelJS you can now activate my plugin babel-plugin-transform-object-from-destructuring (see npm package for installation and usage).
I had the same issue described in this thread and for me it was very exhausting when you create an object from a destructuring expression, especially when you have to rename, add or remove a property. With this plugin maintaining such scenarios gets much more easier for you.
Object example
let myObject = {
test1: "stringTest1",
test2: "stringTest2",
test3: "stringTest3"
};
let { test1, test3 } = myObject,
myTest = { test1, test3 };
can be written as:
let myTest = { test1, test3 } = myObject;
Array example
let myArray = ["stringTest1", "stringTest2", "stringTest3"];
let [ test1, , test3 ] = myArray,
myTest = [ test1, test3 ];
can be written as:
let myTest = [ test1, , test3 ] = myArray;
It's totally possible. Just not in one statement.
var foo = {
x: "bar",
y: "baz"
};
var oof = {};
({x: oof.x, y: oof.y} = foo); // {x: "bar", y: "baz"}
(Do note the parenthesis around the statement.)
But keep in mind legibility is more important than code-golfing :).
Source: http://exploringjs.com/es6/ch_destructuring.html#sec_assignment-targets
You can just use restructuring for that like this:
const foo = {x:"a", y:"b"};
const {...oof} = foo; // {x:"a", y:"b"}
Or merge both objects if oof has values:
const foo = {x:"a", y:"b"};
let oof = {z:"c"}
oof = Object.assign({}, oof, foo)
You can return the destructured object in an arrow function, and use Object.assign() to assign it to a variable.
const foo = {
x: "bar",
y: "baz"
}
const oof = Object.assign({}, () => ({ x, y } = foo));
You can destruct an object assigning directly to another object attribute.
Working example:
let user = {};
[user.name, user.username] = "Stack Overflow".split(' ');
document.write(`
1st attr: ${user.name} <br />
2nd attr: ${user.username}`);
You can work with destructing using variables with the same name of object attribute you want to catch, this way you don't need to do:
let user = { name: 'Mike' }
let { name: name } = user;
Use this way:
let user = { name: 'Mike' }
let { name } = user;
The same way you can set new values to object structures if they have the same attribute name.
Look this working example:
// The object to be destructed
let options = {
title: "Menu",
width: 100,
height: 200
};
// Destructing
let {width: w, height: h, title} = options;
// Feedback
document.write(title + "<br />"); // Menu
document.write(w + "<br />"); // 100
document.write(h); // 200
Try
var a = {a1:1, a2: 2, a3: 3};
var b = {b1:1, b2: 2, b3: 3};
const newVar = (() => ({a1, a2, b1, b2})).bind({...a, ...b});
const val = newVar();
console.log({...val});
// print: Object { a1: 1, a2: 2, b1: 1, b2: 2 }
or
console.log({...(() => ({a1, a2, b1, b2})).bind({...a, ...b})()});
I came up with this method:
exports.pick = function pick(src, props, dest={}) {
return Object.keys(props).reduce((d,p) => {
if(typeof props[p] === 'string') {
d[props[p]] = src[p];
} else if(props[p]) {
d[p] = src[p];
}
return d;
},dest);
};
Which you can use like this:
let cbEvents = util.pick(this.props.events, {onFocus:1,onBlur:1,onCheck:'onChange'});
let wrapEvents = util.pick(this.props.events, {onMouseEnter:1,onMouseLeave:1});
i.e., you can pick which properties you want out and put them into a new object. Unlike _.pick you can also rename them at the same time.
If you want to copy the props onto an existing object, just set the dest arg.
This is kind of cheating, but you can do something like this...
const originalObject = {
hello: 'nurse',
meaningOfLife: 42,
your: 'mom',
};
const partialObject = (({ hello, your }) => {
return { hello, your };
})(originalObject);
console.log(partialObject); // { hello: 'nurse', your: 'mom' }
In practice, I think you'd rarely want to use that though. The following is MUCH more clear... but not nearly as fun.
const partialObject = {
hello: originalObject.hello,
your: originalObject.your,
};
Another completely different route, which includes mucking with the prototype (careful now...):
if (!Object.prototype.pluck) {
Object.prototype.pluck = function(...props) {
return props.reduce((destObj, prop) => {
destObj[prop] = this[prop];
return destObj;
}, {});
}
}
const originalObject = {
hello: 'nurse',
meaningOfLife: 42,
your: 'mom',
};
const partialObject2 = originalObject.pluck('hello', 'your');
console.log(partialObject2); // { hello: 'nurse', your: 'mom' }
This is the most readable and shortest solution I could come up with:
let props = {
isValidDate: 'yes',
badProp: 'no!',
};
let { isValidDate } = props;
let newProps = { isValidDate };
console.log(newProps);
It will output { isValidDate: 'yes' }
It would be nice to some day be able to say something like let newProps = ({ isValidDate } = props) but unfortunately it is not something ES6 supports.
You can use JSON class methods to achieve it as follows
const foo = {
x: "bar",
y: "baz"
};
const oof = JSON.parse(JSON.stringify(foo, ['x','y']));
// output -> {x: "bar", y: "baz"}
Pass properties that need to be added to the resulting object as second argument to stringify function in an array format.
MDN Doc for JSON.stringify
This works in chrome 53.0.2785.89
let foo = {
x: "bar",
y: "baz"
};
let oof = {x, y} = foo;
console.log(`oof: ${JSON.stringify(oof)}`);
//prints oof: { "x": "bar", "y": "baz"}
It's not a beautiful way, nor I recommend it, but it's possible this way, just for knowledge.
const myObject = {
name: 'foo',
surname: 'bar',
year: 2018
};
const newObject = ['name', 'surname'].reduce(
(prev, curr) => (prev[curr] = myObject[curr], prev),
{},
);
console.log(JSON.stringify(newObject)); // {"name":"foo","surname":"bar"}
This question already has answers here:
Remove property for all objects in array
(18 answers)
Closed 2 years ago.
I am trying to remove a property from an object array.
export class class1 {
prop1: string;
prop2: string;
prop3: string;
}
export class class2 {
myprop = [
{ prop1:'A', prop2:"1", prop3:"descr1" },
{ prop1:'B', prop2:"2", prop3:"descr2" },
{ prop1:'C', prop2:"3", prop3:"descr3" },
];
get(): class1[] {
return this.myprop ;
}
add(value: class1): void {
this.myprop.push(value);
}
}
var var1 = class2.get();
var var2 =
I would like var2 contain something like this.
[
{ prop1:'A', prop3:"descr1" },
{ prop1:'B', prop3:"descr2" },
{ prop1:'C', prop3:"descr3" },
];
Is there a way to convert/cast var1 into the above? In other words, I would like to remove prop2 from var1 object array and assign it to var2. How can I do that?
This seems like a great time to use .map()
var var1 = class2.get();
var var2 = var1.map(obj => ({prop1: obj.prop1, prop3: obj.prop3}));
Short, sweet, and does what you want.
MDN docs for .map()
You can delete object property like this e.g.
var myprop = [
{prop1: 'A', prop2: "1", prop3: "descr1"},
{prop1: 'B', prop2: "2", prop3: "descr2"},
{prop1: 'C', prop2: "3", prop3: "descr3"},
];
myprop = myprop.filter(function (props) {
delete props.prop2;
return true;
});
console.log(myprop);
Casting in TypeScript won't remove the property but only hide it in your IDE because it will be compile to JavaScript for runtime.
First of all, if you don't want to remove prop2 from var1 while deleting the property from var2 you need to clone it. For that you will need this JavaScript function:
function cloneObject(obj) {
if (obj === null || typeof obj !== 'object') {
return obj;
}
var temp = obj.constructor(); // give temp the original obj's constructor
for (var key in obj) {
temp[key] = cloneObject(obj[key]);
}
return temp;
}
Use the clone function to clone var1 and loop each object in var2 to remove property prop2. You can do so with JavaScript by combining array.forEach and delete:
var var2 = cloneObject(var1);
var2.forEach((obj) => { delete obj.prop2; });
Doing so will KEEP prop2 in var1 but REMOVE it from var2
// Use delete:
var user = {
firstname:"Jack",
lastname:"Prince",
};
var result = delete user.firstname;
console.log(result,"firstname deleted");
console.log(user);
//using Object rest spread operator
const { firstname, ...data } = user;
console.log(data);