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Copy array by value
...ually show that var arr2 = arr1.slice() is just as fast as var arr2 = arr1.concat(); JSPerf: jsperf.com/copy-array-slice-vs-concat/5 and jsperf.com/copy-simple-array . The result of jsperf.com/array-copy/5 kind of surprised me to the point I am wondering if the test code is valid.
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How to skip over an element in .map()?
...urce and returns something that looks like the accumulator
// 1. create a concat reducing function that can be passed into `reduce`
const concat = (acc, input) => acc.concat([input])
// note that [1,2,3].reduce(concat, []) would return [1,2,3]
// transforming your reducing function by mapping
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Appending to an existing string
... How do you do s <<! "bar", as in to modify the state of the object? concat!("bar") doesn't work...
– xxjjnn
Dec 21 '12 at 11:32
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How do I concatenate two strings in C?
...of char that is terminated by the first null character. There is no string concatenation operator in C.
Use strcat to concatenate two strings. You could use the following function to do it:
#include <stdlib.h>
#include <string.h>
char* concat(const char *s1, const char *s2)
{
char...
How do I modify fields inside the new PostgreSQL JSON datatype?
... required to manipulate json values).
Merging 2 (or more) JSON objects (or concatenating arrays):
SELECT jsonb '{"a":1}' || jsonb '{"b":2}', -- will yield jsonb '{"a":1,"b":2}'
jsonb '["a",1]' || jsonb '["b",2]' -- will yield jsonb '["a",1,"b",2]'
So, setting a simple key can be done using:...
ROW_NUMBER() in MySQL
...s you could do something like this:
SELECT @row_num := IF(@prev_value=concat_ws('',t.col1,t.col2),@row_num+1,1) AS RowNumber
,t.col1
,t.col2
,t.Col3
,t.col4
,@prev_value := concat_ws('',t.col1,t.col2)
FROM table1 t,
(SELECT @row_num := ...
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 ...
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
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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...
byte[] to hex string [duplicate]
...verting bytes to a string would be so much slower. You weren't using += to concatenate the strings together, were you?
– Guffa
Nov 23 '15 at 22:29
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