JavaScript: Unterschied zwischen den Versionen
Zur Navigation springen
Zur Suche springen
(→String) |
|||
Zeile 1: | Zeile 1: | ||
[[Kategorie:Sprache]] | [[Kategorie:Sprache]] | ||
= | = Links = | ||
* [[JavaScript_HTML_DOM]] | |||
= Methoden = | = Methoden = |
Version vom 27. August 2018, 08:45 Uhr
Links
Methoden
var hypotenuse = function(a,b) { return Math.sqrt(a*a+b*b); } console.log(hypotenuse(1, 44)); var addAll = function(){ var rc=0; for (var ix=0; ix < arguments.length; ix++) rc += arguments[ix]; return rc; } addAll(1, 2, 3) === 6;
Strikte Gleichheit
- a == b: Referenzvergleich
- a === b: Inhaltsvergleich
Typen
String
text += "."; "xyz".substr(1, 2) === "y"; "abc".indexOf("bc") === 1; "abab".indexOf("a", 1) == 2; "abcb".replace("b", "x") === "axcb"; "a".toUpperCase() === "A"; "A".toLowerCase() === "a"; "abc".length === 3; "abc".charAt(1) == "b"; " abc ".trim() = "abc";
Numbers
- Nur Gleitpunktzahlen werden benutzt.
- Daher haben Ganzzahlen max. 53 Bit
- x=Math.min(1,2,3); r=Math.floor(x); w=Math.sqrt(x);
- var undef = NaN;
- isNaN(1/0) === true;
- y = parseInt("123");
- str = 123.toString();
Datum
var now = new Date(); var x = new Date(2018, 0, 3, 22, 33, 44, 117); /// !!! Monat ab 0 gezählt!!! var year33Since1970 = new Date(24*3600*365.25 * 33); var z = new Date("2017-3-8T16:31:10.117"); 2017 === z.getFullYear(); 2===z.getMonth(); 8===z.getDate(); 16===z.getHours(); 31==z.getMinutes(); 10===z.getSeconds(); 117===z.getMilliseconds(); z.setHours(3); z.setMinutes(9); z.setSeconds(33); z.setMilliseconds(118); var utc = new Date(Date.UTC(2018, 4, 6)); var millisSince1970 = utc.getTime();
Dictionary
var x = { "zahl" : 33, "pair" : { "x" : true } };
Arrays
a=[1, 2, "wow"]; a0=a.shift(); a === [2, "wow"]; a.push(99); a === [2, "wow", 99]; a.concat([2, 3]) === [2, "wow", 99, 2, 3]; [1, 3, 5, 9].slice(0,2) === [1, 3] && [1, 3, 5, 9].slice(2,3) === [3]; [3, 9, 12].join(" ") === "3 9 12";
Klassen
'use strict'; class Polygon { constructor(height, width) { this.name = 'Polygon'; this.height = height; this.width = width; } sayName() { ChromeSamples.log('Hi, I am a ', this.name + '.'); } sayHistory() { ChromeSamples.log('"Polygon" is derived from the Greek polus (many) ' + 'and gonia (angle).'); } static className() { return "Polygon"; } } const p = new Polygon(300, 400); p.sayName();