I was asked to define a function that would accept an array of strings, and use the map method to create another array with the trimmed strings.
My output trimmed the strings, however, it still said it was wrong. Can anyone tell me why?
function cleanNames(){
let cleanNames = [" Eric", " Nanci", " Luna"];
let trimmedNames = cleanNames.map(function (elem) {
console.log(elem.trim());
});
}
You need to return the trimmed string in the map function.
array.map(function(ele){
return ele.trim();
})
You've almost got it, but you're missing two return statements. Since this sounds like homework, I'll let you figure out where.
You can try something like:
const cleanNames = () => {
/* you declare your variables */
const names = [" Eric", " Nanci", " Luna"];
/* You map your array */
names.map((el) => {
/* You access each index and cut the blank spaces with the Trim () method */
console.log(el.trim())
})
}
/* You call your function */
cleanNames()
This will work to you. The problem is because you are not expecting an array and you are not returning the new array with the new array of trimmed strings
function trimFunc(stringArray) {
return stringArray.map(string => string.trim());
}
try the below solution:
function cleanNames(arr) {
return arr.map(i => i.trim());
}
console.log(cleanNames(['njue', ' kamau', ' kimani','kalonzo']));
Related
So I want to create a dynamic key in a js object. I know I can create it like this but id doesn't fullfil my requirements
return {
[dynamicKey]: value
}
But the problem is I want something like this
return {
[dynamicKey]_id: value
}
but it doesn't let me, I tried concatenating but it didn't work.
return {
[dynamicKey] + '_id': value
}
I've also searched online for a solution but couldn't find any.
you need to put your _id string inside of the square brackets or as part of the dinamicKey var.
return {
[dinamicKey + '_id']: value
}
dinamicKey += '_id';
return {
[dinamicKey]: value
}
Any expression in the square braces will be executed just like a normal expression.
So how about this:
return {
[dinamicKey + '_id']: value
}
Currently, I have a huge JavaScript array where each element is like this:
[{"open":235.86,
"high":247.13,
"low":231.5,
"close":244.1,
"volume":55025735,
"date":"2019-05-01T21:00:00.000Z"}
...
I need to remove everything except the price after high. What is the most efficient way I can do this?
I've tried popping the individual elements, but I can't help but feel as if there is a more efficient/easier way to do this.
So hopefully the ending array would just be [235.86].
The below code should work. It's efficient enough :D
for (i in arrayName){
// Loops through array
delete arrayName[i].high
delete arrayName[i].low
delete arrayName[i].close
delete arrayName[i].volume
delete arrayName[i].date
// Deletes unwanted properties
}
console.log(arrayName)
// Print output
One potential solution would be to map the array to a new array like so:
const yourArray = [
{"open":235.86, "high":247.13, "low":231.5, "close":244.1, "volume":55025735},
{"open":257.52, "high":234.53, "low":220.2, "close":274.1, "volume":23534060},
]
const mappedArray = yourArray.map(el => el.open);
// mappedArray = [235.86, 257.52]
Check out the MDN documentation for the map method, Array.prototype.map()
Note: The above example uses ECMAScript 6 arrow functions and implicit returns. It is functionally equivalent to:
const yourArray = [
{"open":235.86, "high":247.13, "low":231.5, "close":244.1, "volume":55025735},
{"open":257.52, "high":234.53, "low":220.2, "close":274.1, "volume":23534060},
]
const mappedArray = yourArray.map(function(el){
return el.open
});
You can use reduce for this scenario. Example
var temp = [{"open":235.86, "high":247.13, "low":231.5, "close":244.1, "volume":55025735, "date":"2019-05-01T21:00:00.000Z"}];
var highValArray = temp.reduce((arr, t) => {
return arr.concat(t['high']);
}, []);
You can learn more about reduce function at the MDN website.
This should work:
your_array.map((item) => {
return item.high
})
I have an array of strings like so: ['foo', 'bar', 'foo/*/test'] and a random URL like this: http://www.example.com/foo/bar?test=123/another=one#test.
The URL may or may not contain a query or a hash prop.
Is there a regex or simple functionality to check the URL, in the URL contains any of those values in the array?
I am aware of the String.prototype.includes function so we could just do:
let path = location.pathname and then path.includes('foo'), but I want strings that contain the structure of foo/*/bar/ to be of higher importance.
For example if the URL is like this: http://www.example.com/foo/1234/test, the function should only return for the value foo/*/test instead of directly return with the foo value inside of the array.
So as soon as I have a string inside of the array which contains a / or something, I want this value to check first or give this the top prio so to speak.
Thanks!
Since the formatting inside a reply is all messed up, I have to post it like this:
#VincentDecaux totally understand.My first thoughts would have been sth like this:
function checkUrl(url, arr) {
const checkForPaths = arr.filter(val => val.match(/[\/](\w+)/ig));
if (checkForPaths.length) {
return true;
}
const filteredArray = arr.filter(val => url.includes(val));
if (filteredArray.length) {
return true;
}
return false;
}
This might already work since I only want the function to return true/false in order to display sth. on the page depemding on this.
I think it should be possible to use map.reduce to transform an array into newline separated string. But for some reason it is not working. What am I doing wrong
copyLicenseCodesToClipboard = () => {
// tslint:disable-next-line:no-any
const licenseCodes = this.props.generateLicenseCodes.reduce((accumulator: any, element: LicenseCode) =>
accumulator.concat(element.code).concat('\n')
);
copyToClipboard(JSON.stringify(licenseCodes));
}
Uncaught TypeError: accumulator.concat is not a function
You can also use map and join, which seems to be more intuitive in this case.
const licenseCodes = this.props.generateLicenseCodes.map((element)=>{return element.code;}).join("\n");
Script
var companies=[
{name:'Vicky',category:'Devdas',start:1993,end:2090},
{name:'Vikrant',category:'Devdas',start:1994,end:2019},
{name:'Akriti',category:'mental',start:1991,end:2021},
{name:'Dummy',category:'dummyCategory',start:1995,end:2018},
{name:'Dummy 1',category:'dummyCategory',start:1993,end:2029}
];
var mappingComp=companies.map(company=>{company.start+10;return company});
console.log("mapped company function");
console.log(mappingComp.forEach(company=>console.log(company)));
In the above snippet there is no change in start field of companies array . Why ?
In case I do below I do get modified values for start field from companies array.
var mappingComp=companies.map(company=>company.start+10);
You aren't assigning the result of company.start+10 to anything - it's just an orphaned expression.
var mappingComp = companies.map(company => {
company.start + 10;
return company
});
is just like
var mappingComp = companies.map(company => {
33;
return company
});
The expression is evaluated to a value and then discarded. If you want to add 10 to company.start, use += or =:
var companies=[
{name:'Vicky',category:'Devdas',start:1993,end:2090},
{name:'Vikrant',category:'Devdas',start:1994,end:2019},
{name:'Akriti',category:'mental',start:1991,end:2021},
{name:'Dummy',category:'dummyCategory',start:1995,end:2018},
{name:'Dummy 1',category:'dummyCategory',start:1993,end:2029}
];
var mappingComp = companies.map(company => {
company.start += 10;
return company;
});
console.log(mappingComp);
But this will mutate the original array, which is (often) not a great idea when using map. If you don't want to change the original array, map to a new object:
var companies=[
{name:'Vicky',category:'Devdas',start:1993,end:2090},
{name:'Vikrant',category:'Devdas',start:1994,end:2019},
{name:'Akriti',category:'mental',start:1991,end:2021},
{name:'Dummy',category:'dummyCategory',start:1995,end:2018},
{name:'Dummy 1',category:'dummyCategory',start:1993,end:2029}
];
var mappingComp = companies.map(({ start, ...rest }) => ({
start: start + 10,
...rest
}));
console.log(mappingComp);
company.start + 10 is a simple expression. It's not an assignment statement, that you are expecting it to be. And you are returning the initial array company so it makes sense that it will be returned unaltered.
when you tried the single line fat arrow function with the map. What happens is that you created another entirely different array of mutated values. The array created was populated with values (company.start +10) and returned. Note: This actually didn't change the initial array ie company.
Read up on fat arrow functions, map, filter.