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How to check a not-defined variable in JavaScript
...cript 5, which was released in 2009. You can now safely use === and !== to test for undefined without using typeof as undefined has been read-only for some time.
If you want to know if a member exists independent but don't care what its value is:
if ('membername' in object) // With inheritance
if ...
BSS段、数据段、代码段、堆与栈 剖析 - C/C++ - 清泛网 - 专注C/C++及内核技术
...化，因此造成了上述情况。
【例二】
编译如下程序（test.cpp）：
#include <stdio.h>
#define LEN 1002000
int inbss[LEN];
float fA;
int indata[LEN]={1,2,3,4,5,6,7,8,9};
double dbB = 100.0;
const int cst = 100;
int main(void)
{
int run[100] = {1,2,3,4,5,6,7,8,9};
...
Checking for a dirty index or untracked files with Git
...s
My first thought is to just check whether these commands have output:
test -z "$(git ls-files --others)"
If it exits with 0 then there are no untracked files. If it exits with 1 then there are untracked files.
There is a small chance that this will translate abnormal exits from git ls-file...
Detect changes in the DOM
...l = document.documentElement;
var remain = 3;
// callback for the tests
function decide() {
if (support.DOMNodeInserted) {
window.addEventListener("DOMContentLoaded", function () {
if (support.DOMSubtreeModified) { // for FF 3+, Chrome
...
How do I set up a basic Ruby project?
...ct with 10 ~ 20 classes/files. I need some gems and I want to use RSpec as test framework.
4 Answers
...
How to run Selenium WebDriver test cases in Chrome?
...
Outdated again on 23 March. Unable to use on the latest Chrome.
– willem
Mar 23 '17 at 9:20
add a comment
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ruby system command check exit code
...
If you are in a rails console, testing this out, just keep in mind you may lose the value of $? so you need to capture it as part of your REPL command [10] pry(main)> system("touch /root/test 2> /dev/null") => false [11] pry(main)> $?.exitstat...
Get the index of the object inside an array, matching a condition
...big arrays a simple loop will perform much better than findIndex:
let test = [];
for (let i = 0; i < 1e6; i++)
test.push({prop: i});
let search = test.length - 1;
let count = 100;
console.time('findIndex/predefined function');
let fn = obj => obj.prop === search;
...
Truncating all tables in a Postgres database
...= 'public'
LOOP
RAISE NOTICE '%',
-- EXECUTE -- dangerous, test before you execute!
format('TRUNCATE TABLE %I.%I CASCADE', _sch, _tbl);
END LOOP;
END
$func$ LANGUAGE plpgsql;
format() requires Postgres 9.1 or later. In older versions concatenate the query string like th...
How to escape double quotes in a title attribute
... Yep. <a href="#" title="Foo &quot;Bar&quot;">Testing</a> and <a href="#" title="Smart quotes &#8221;Bar&#8220;">Testing too</a> work for me.
– Olly Hodgson
Sep 20 '10 at 15:17
...