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Why is [1,2] + [3,4] = “1,23,4” in JavaScript?
...r arrays.
What happens is that Javascript converts arrays into strings and concatenates those.
Update
Since this question and consequently my answer is getting a lot of attention I felt it would be useful and relevant to have an overview about how the + operator behaves in general also.
So, here ...
what is the preferred way to mutate a React state?
...
concat returns a new array, so you can do
this.setState({list: this.state.list.concat([newObject])});
another alternative is React's immutability helper
var newState = React.addons.update(this.state, {
list : {
...
how to get the host url using javascript from the current page
... possibly
var host = "http://"+window.location.hostname;
or if you like concatenation
var protocol = location.protocol;
var slashes = protocol.concat("//");
var host = slashes.concat(window.location.hostname);
share
...
Best way to combine two or more byte arrays in C#
...yield operator - 0.0781270 seconds
IEnumerable<byte> using LINQ's Concat<> - 0.0781270 seconds
I increased the size of each array to 100 elements and re-ran the test:
New Byte Array using System.Array.Copy - 0.2812554 seconds
New Byte Array using System.Buffer.BlockCop...
How to store arrays in MySQL?
... AS pfs_person_name,
cast(concat('[', group_concat(json_quote(fruit_name) ORDER BY fruit_name SEPARATOR ','), ']') as json) AS pfs_fruit_name_array
FROM
person
INNER JOIN person_fruit
ON person.person_id = person_fruit.pf_person
IN...
Create a list from two object lists with linq
...
For reference: there's also Concat that doesn't merge duplicates
– Kos
Apr 15 '12 at 10:12
...
Concat scripts in order with Gulp
...mque module which has worked quite well for specifying order of in my case concatenation. https://github.com/gulpjs/gulp/blob/master/docs/recipes/using-multiple-sources-in-one-task.md
Example of how I used it is below
var gulp = require('gulp');
var concat = require('gulp-concat');
v...
Unique random string generation
...e.MaxValue + 1 - (byte.MaxValue + 1) % alphabet.Length;
return string.Concat(
Enumerable
.Repeat(0, int.MaxValue)
.Select(e => RandomByte())
.Where(randomByte => randomByte < outOfRange)
.Take(length)
.Select(randomByt...
How to process POST data in Node.js?
...hunks.push(chunk));
request.on('end', () => {
const data = Buffer.concat(chunks);
console.log('Data: ', data);
})
}).listen(8080)
Here Buffer.concat is used, which simply concatenates all buffers and return one big buffer. You can also use the concat-stream module which does the sam...
convert string array to string
...er option than using the already mentioned use of the Join() method is the Concat() method. It doesn't require an empty delimiter parameter as Join() does. Example:
string[] test = new string[2];
test[0] = "Hello ";
test[1] = "World!";
string result = String.Concat(test);
hence it is likely fast...