No error , No gain

How do I check if a particular key exists in a JavaScript object or array? If a key doesn't exist, and I try to access it, will it return false? Or throw an error? Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You s..

I know how to make a new branch that tracks remote branches, but how do I make an existing branch track a remote branch? I know I can just edit the .git/config file, but it seems there should be an easier way. Given a branch foo and a remote upstream: As of Git 1.8.0: git branch -u upstream/foo Or, if local branch foo is not the current branch: git branch -u upstream/foo foo Or, if you like to t..

I would like to know how to delete a commit. By delete, I mean it is as if I didn't make that commit, and when I do a push in the future, my changes will not push to the remote branch. I read git help, and I think the command I should use is git reset --hard HEAD. Is this correct? Careful: git reset --hard WILL DELETE YOUR WORKING DIRECTORY CHANGES. Be sure to stash any local changes you want to..

How can I stash only one of multiple changed files on my branch? git stash push -p -m "my commit message" -p let's you select the hunks that should be stashed; whole files can be selected as well. You'll be prompted with a few actions for each hunk: y - stash this hunk n - do not stash this hunk q - quit; do not stash this hunk or any of the remaining ones a - stash this hunk and all later hunks..

This question's answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions. How can I list all files of a directory in Python and add them to a list? os.listdir() will get you everything that's in a directory - files and directories. If you want just files, you could either filter this down using os.path: from os import l..

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python? >>> ["foo", "bar", "baz"].index("bar") 1 Reference: Data Structures > More on Lists Caveats follow Note that while this is perhaps the cleanest way to answer the question as asked, index is a rather weak component of the list API, and I can't remember the last time I used it in anger. It's bee..

I've always been one to simply use: List names = new ArrayList(); I use the interface as the type name for portability, so that when I ask questions such as these I can rework my code. When should LinkedList be used over ArrayList and vice-versa? Summary ArrayList with ArrayDeque are preferable in many more use-cases than LinkedList. If you're not sure — just start with ArrayList. TLDR, in Array..

I've used the following script to see if a file exists: #!/bin/bash FILE=$1 if [ -f $FILE ]; then echo "File $FILE exists." else echo "File $FILE does not exist." fi What's the correct syntax to use if I only want to check if the file does not exist? #!/bin/bash FILE=$1 if [ $FILE does not exist ]; then echo "File $FILE does not exist." fi The test command ([ here) has a "not" logical operator w..

In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance? The official tutorial may be of some use to you. Class Package Subclass (same pkg) Subclass (diff pkg) World public + + + + + protected + + + + no modifier + + + private + + : accessible blank :..

I have an array of JavaScript objects: var objs = [ { first_nom: 'Lazslo', last_nom: 'Jamf' }, { first_nom: 'Pig', last_nom: 'Bodine' }, { first_nom: 'Pirate', last_nom: 'Prentice' } ]; How can I sort them by the value of last_nom in JavaScript? I know about sort(a,b), but that only seems to work on strings and numbers. Do I need to add a toString() method to my objects? It's easy enough to writ..