Tutorial by Examples: in

This example assumes Ruby and Ruby on Rails have already been installed properly. If not, you can find how to do it here. Open up a command line or terminal. To generate a new rails application, use rails new command followed by the name of your application: $ rails new my_app If you want to c...

Continuing a "for" Loop When you put the continue keyword in a for loop, execution jumps to the update expression (i++ in the example): for (var i = 0; i < 3; i++) { if (i === 1) { continue; } console.log(i); } Expected output: 0 2 Continuing a While...

Using the def statement is the most common way to define a function in python. This statement is a so called single clause compound statement with the following syntax: def function_name(parameters): statement(s) function_name is known as the identifier of the function. Since a function def...

Functions can return a value that you can use directly: def give_me_five(): return 5 print(give_me_five()) # Print the returned value # Out: 5 or save the value for later use: num = give_me_five() print(num) # Print the saved returned value # Out: 5 or use the value f...

Decorators normally strip function metadata as they aren't the same. This can cause problems when using meta-programming to dynamically access function metadata. Metadata also includes function's docstrings and its name. functools.wraps makes the decorated function look like the original function b...

Sometimes you don't want to have your function accessible/stored as a variable. You can create an Immediately Invoked Function Expression (IIFE for short). These are essentially self-executing anonymous functions. They have access to the surrounding scope, but the function itself and any internal va...

When you define a function, it creates a scope. Everything defined within the function is not accessible by code outside the function. Only code within this scope can see the entities defined inside the scope. function foo() { var a = 'hello'; console.log(a); // => 'hello' } consol...

The then method of a promise returns a new promise. const promise = new Promise(resolve => setTimeout(resolve, 5000)); promise // 5 seconds later .then(() => 2) // returning a value from a then callback will cause // the new promise to resolve with this value .then...

A Promise object represents an operation which has produced or will eventually produce a value. Promises provide a robust way to wrap the (possibly pending) result of asynchronous work, mitigating the problem of deeply nested callbacks (known as "callback hell"). States and control flow ...

Integers in PHP can be natively specified in base 2 (binary), base 8 (octal), base 10 (decimal), or base 16 (hexadecimal.) $my_decimal = 42; $my_binary = 0b101010; $my_octal = 052; $my_hexadecimal = 0x2a; echo ($my_binary + $my_octal) / 2; // Output is always in decimal: 42 Integers are 3...

In addition to the built-in round function, the math module provides the floor, ceil, and trunc functions. x = 1.55 y = -1.55 # round to the nearest integer round(x) # 2 round(y) # -2 # the second argument gives how many decimal places to round to (defaults to 0) round(x, 1) ...

Sometimes, when you have local changes incompatible with remote changes (ie, when you cannot fast-forward the remote branch, or the remote branch is not a direct ancestor of your local branch), the only way to push your changes is a force push. git push -f or git push --force Important not...

import random randint() Returns a random integer between x and y (inclusive): random.randint(x, y) For example getting a random number between 1 and 8: random.randint(1, 8) # Out: 8 randrange() random.randrange has the same syntax as range and unlike random.randint, the last value is no...

git log --oneline will show all of your commits with only the first part of the hash and the commit message. Each commit will be in a single line, as the oneline flag suggests. The oneline option prints each commit on a single line, which is useful if you’re looking at a lot of commits. - sou...

break statement When a break statement executes inside a loop, control flow "breaks" out of the loop immediately: i = 0 while i < 7: print(i) if i == 4: print("Breaking from loop") break i += 1 The loop conditional will not be evaluated a...

Standard Creation It is recommended to use this form only when creating regex from dynamic variables. Use when the expression may change or the expression is user generated. var re = new RegExp(".*"); With flags: var re = new RegExp(".*", "gmi"); With a backsl...

Match Using .exec() RegExp.prototype.exec(string) returns an array of captures, or null if there was no match. var re = /([0-9]+)[a-z]+/; var match = re.exec("foo123bar"); match.index is 3, the (zero-based) location of the match. match[0] is the full match string. match[1] is the t...

var re = /[a-z]+/; if (re.test("foo")) { console.log("Match exists."); } The test method performs a search to see if a regular expression matches a string. The regular expression [a-z]+ will search for one or more lowercase letters. Since the pattern matches the string,...

The String object has the following methods that accept regular expressions as arguments. "string".match(... "string".replace(... "string".split(... "string".search(... Match with RegExp console.log("string".match(/[i-n]+/)); console.log(&...

git remote add upstream git-repository-url Adds remote git repository represented by git-repository-url as new remote named upstream to the git repository