Javascript – Get the first integers in a string with JavaScript

javascriptstringstring-formatting

I have a string in a loop and for every loop, it is filled with texts the looks like this:

"123 hello everybody 4"
"4567 stuff is fun 67"
"12368 more stuff"

I only want to retrieve the first numbers up to the text in the string and I, of course, do not know the length.

Thanks in advance!

Best Solution

If the number is at the start of the string:

("123 hello everybody 4").replace(/(^\d+)(.+$)/i,'$1'); //=> '123'

If it's somewhere in the string:

(" hello 123 everybody 4").replace( /(^.+)(\w\d+\w)(.+$)/i,'$2'); //=> '123'

And for a number between characters:

("hello123everybody 4").replace( /(^.+\D)(\d+)(\D.+$)/i,'$2'); //=> '123'

[addendum]

A regular expression to match all numbers in a string:

"4567 stuff is fun4you 67".match(/^\d+|\d+\b|\d+(?=\w)/g); //=> ["4567", "4", "67"]

You can map the resulting array to an array of Numbers:

"4567 stuff is fun4you 67"
  .match(/^\d+|\d+\b|\d+(?=\w)/g)
  .map(function (v) {return +v;}); //=> [4567, 4, 67]

Including floats:

"4567 stuff is fun4you 2.12 67"
  .match(/\d+\.\d+|\d+\b|\d+(?=\w)/g)
  .map(function (v) {return +v;}); //=> [4567, 4, 2.12, 67]

If the possibility exists that the string doesn't contain any number, use:

( "stuff is fun"
   .match(/\d+\.\d+|\d+\b|\d+(?=\w)/g) || [] )
   .map(function (v) {return +v;}); //=> []

So, to retrieve the start or end numbers of the string 4567 stuff is fun4you 2.12 67"

// start number
var startingNumber = ( "4567 stuff is fun4you 2.12 67"
  .match(/\d+\.\d+|\d+\b|\d+(?=\w)/g) || [] )
  .map(function (v) {return +v;}).shift(); //=> 4567

// end number
var endingNumber = ( "4567 stuff is fun4you 2.12 67"
  .match(/\d+\.\d+|\d+\b|\d+(?=\w)/g) || [] )
  .map(function (v) {return +v;}).pop(); //=> 67

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

Javascript – the most efficient way to deep clone an object in JavaScript

Native deep cloning

It's called "structured cloning", works experimentally in Node 11 and later, and hopefully will land in browsers. See this answer for more details.

Fast cloning with data loss - JSON.parse/stringify

If you do not use Dates, functions, undefined, Infinity, RegExps, Maps, Sets, Blobs, FileLists, ImageDatas, sparse Arrays, Typed Arrays or other complex types within your object, a very simple one liner to deep clone an object is:

JSON.parse(JSON.stringify(object))

const a = {
  string: 'string',
  number: 123,
  bool: false,
  nul: null,
  date: new Date(),  // stringified
  undef: undefined,  // lost
  inf: Infinity,  // forced to 'null'
  re: /.*/,  // lost
}
console.log(a);
console.log(typeof a.date);  // Date object
const clone = JSON.parse(JSON.stringify(a));
console.log(clone);
console.log(typeof clone.date);  // result of .toISOString()

See Corban's answer for benchmarks.

Reliable cloning using a library

Since cloning objects is not trivial (complex types, circular references, function etc.), most major libraries provide function to clone objects. Don't reinvent the wheel - if you're already using a library, check if it has an object cloning function. For example,

lodash - cloneDeep; can be imported separately via the lodash.clonedeep module and is probably your best choice if you're not already using a library that provides a deep cloning function
AngularJS - angular.copy
jQuery - jQuery.extend(true, { }, oldObject); .clone() only clones DOM elements
just library - just-clone; Part of a library of zero-dependency npm modules that do just do one thing. Guilt-free utilities for every occasion.

ES6 (shallow copy)

For completeness, note that ES6 offers two shallow copy mechanisms: Object.assign() and the spread syntax. which copies values of all enumerable own properties from one object to another. For example:

var A1 = {a: "2"};
var A2 = Object.assign({}, A1);
var A3 = {...A1};  // Spread Syntax