I'm building a logger service. First argument is "msg" string and the second one in array of parameters (can be array or objects)
How can i iterate this parameters array and print in the console so the object/array can be seen\expand\collapse in the console?
For example if it's not dynamic i would do something like this:
console.log('str', obj1, obj2, obj3)
You mean something like this?
let arrayOfObjects = [
{ a: 1, b: 2 },
{ a: 3, b: 4, c: 5 }
];
let testMessage = "This is just a message";
console.log(testMessage, Object.values(arrayOfObjects));
Related
I have an Object
let data = {
a: 1,
b: 2,
c: {
abc: "ak",
bcd: "gh",
cfv: "ht"
}
}
then I have variables which I need to show with these object value
let abc = "first 1", bcd="sec2", cfv="third3" , def="fourth 4", tdf = "fifth 5";
Now the Object will come in API call it can be any of these variable.
How can I match the variable name with the object data.c.(object key) and concatinate their value.
for example the output should be
As we have (abc, bcd, cfv) as our object key then the output would be
first 1ak ==> that is the value of (abc + data.c["abc"])
sec2gh ==> that is the value of (bcd + data.c["bcd"])
third3ht ==> that is the value of (cfv + data.c["cfv"])
I tried using Object.keys() method so from this method we will get the object keys in array then how can I match with the variable name -
Object.keys(data.c);
==> ["abc", "bcd", "cfv"] (After this how can I proceed to match the variable and show their values?)
Shall I loop throught the object that (data.c)?
Please help me giving some ideas to achieve this implementation.
thank you
If it's possible for you to amend the format of your abc, bcd etc. variables to be the properties in an object, then this problem becomes trivial. You can use flatMap() to create a new array of the output values by linking the properties of the two target objects, like this:
let values = {
abc: "first 1",
bcd: "sec2",
cfv: "third3",
def: "fourth 4",
tdf: "fifth 5"
}
let data = {
a: 1,
b: 2,
c: {
abc: "ak",
bcd: "gh",
cfv: "ht"
}
}
let output = Object.keys(values).flatMap(k => data.c.hasOwnProperty(k) ? values[k] + data.c[k] : []);
console.log(output);
Object.assign(...as) appears to change the input parameter. Example:
const as = [{a:1}, {b:2}, {c:3}];
const aObj = Object.assign(...as);
I deconstruct an array of object literals as parameter of the assign function.
I omitted console.log statements. Here's the stdout from node 13.7:
as before assign: [ { a: 1 }, { b: 2 }, { c: 3 } ]
aObj: { a: 1, b: 2, c: 3 }
as after assign: [ { a: 1, b: 2, c: 3 }, { b: 2 }, { c: 3 } ]
The reader may notice that as first element has been changed in an entire.
Changing a new array bs elements to an immutable object (using freeze)
const bs = [{a:1}, {b:2}, {c:3}];
[0, 1, 2].map(k => Object.freeze(bs[k]));
const bObj = Object.assign(...bs);
leads to an error:
TypeError: Cannot add property b, object is not extensible
at Function.assign (<anonymous>)
Which indicates the argument is indeed being changed.
What really confounds me is that even binding my array, cs, by currying it to a function (I think you call this a closure in JS)
const cs = [{a:1}, {b:2}, {c:3}];
const f = (xs) => Object.assign(...xs);
const g = () => f(cs);
const cObj = g();
returns:
cs before assign: [ { a: 1 }, { b: 2 }, { c: 3 } ]
cObj: { a: 1, b: 2, c: 3 }
cs after assign: [ { a: 1, b: 2, c: 3 }, { b: 2 }, { c: 3 } ]
What went wrong here? And how may one safely use Object.assign without wrecking its first argument?
Object.assign is not a pure function, it writes over its first argument target.
Here is its entry on MDN:
Object.assign(target, ...sources)
Parameters
target
The target object — what to apply the sources’ properties to, which is returned after it is modified.
sources
The source object(s) — objects containing the properties you want to apply.
Return value
The target object.
The key phrase is "[the target] is returned after it is modified". To avoid this, pass an empty object literal {} as first argument:
const aObj = Object.assign({}, ...as);
I have two arrays; one with substrings and the other with objects.
I would like to obtain an array of objects where those objects contain any of the substrings in the substrings array.
So far I have tried to use filter and findIndex. Each approach works if a substring is identical. In this case, even indexOf was not working. I am not javascript guy, so probably I am doing something wrong.
Script
var strings = ['12', 'sv', 'eli', '23', '34'];
var data = [
{
a: 349531284734,
b: "sv123eippppppeli",
c: "aaabbbccc"
},
{
a: 1111123333312,
b: "ccccccccccccs2222",
c: "aaabbbccc"
},
{
a: 2222234,
b: "elllllllla",
c: false
},
];
// attempt 1
var results = data.filter(arr =>
Object.keys(arr).some(key => {
return String(arr[key]).toLowerCase().includes(strings) // or indexOf
})
);
// attempt 2 with only one data index
var obj = Object.values(data[0]);
var results = strings.some(s => obj.includes(s)) // or indexOf or findIndex;
Explanation
In this example with the given substrings, only data[0] is a match because it contains at least on of the substrings in the strings array.
How can I make this work without using a "for loop"?
Thanks
A simple solution that avoids the need for "for-loop" syntax would be to filter() each object of data by a predicate that checks if any value (of the current item being filtered) contains any one of the values of the strings array.
In code, this can be expressed as:
var strings = ['12', 'sv', 'eli', '23', '34'];
var data = [{
a: 349531284734,
b: "sv123eippppppeli",
c: "aaabbbccc"
},
{
a: 1111123333312,
b: "ccccccccccccs2222",
c: "aaabbbccc"
},
{
a: 2222234,
b: "elllllllla",
c: false
},
];
// Local helper retruns true if case-insenstive value in strings array
const stringHasValue = (value) => strings
.some(str => value.toLowerCase().includes(str.toLowerCase()))
// Filter each item in data array by existance of a value containing
// substring in strings array
var result = data.filter((item) => Object.values(item)
.filter(value => typeof value === 'string')
.some(stringHasValue, []));
console.log(result);
For example I want something like:
{
a: 1,
b: 2,
c: 3
}
turned into:
{
d: {
a: 1,
b: 2,
c: 3
}
}
I've tried assigning a new property to that object with the object itself but it shows up as circular so I figure it's a reference instead of the actual properties instead of the actual values. I want to try something like JSON.stringify the object and assign it to the property but I don't know how to turn that string into an object format that I can assign to the property.
let firstObj = {
a: 1,
b: 2,
c: 3
}
let secondObj = {};
secondObj.d = firstObj;
console.log(secondObj);
Basically you create a new object and assign the original object to its property d.
You can use ES6 destructuting to make a shallow copy of the object and put it on a new prop:
let obj = {
a: 1,
b: 2,
c: 3
}
obj.d = {...obj}
console.log(obj)
If that's not an option you can reduce() over the objects keys to make a new object and assign it to d:
let obj = {
a: 1,
b: 2,
c: 3
}
obj.d = Object.keys(obj).reduce((newObj, k) => {
newObj[k] = obj[k]
return newObj
},{})
console.log(obj)
It depends whether you want to make the deep or shallow copy of the object d. (Can the object d have a nested structure?)
The question about efficient ways to clone the object has already been answered here.
I have an object with several nested layers of arrays and subobjects, from which I need to extract the values from some paths. Is there some library or native function which can help me do that? I'm already using Lodash and jQuery, but have a hard time figuring out how to simplify this problem.
Example:
{
a: [
{
b: 0,
c: 1
},
{
b: 1,
c: 2
}
]
}
Now I would like to get a list of all a[0..n].b.
My actual object is much larger and has 3 layers of arrays and a path like syn[0].sem[0].pdtb3_relation[0].sense, so I'd rather not write 3 nested for loops if a library function exists.
You can use forEach() to iterate through array.
var o = {
a: [
{
b: 0,
c: 1
},
{
b: 1,
c: 2
}
]
}
Object.keys(o).forEach(a => o[a].forEach(y => console.log(y.b)));