Differences

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--- lwc:programming:javascript [2020/11/26 22:29] – created John Harrison
+++ lwc:programming:javascript [2025/03/18 13:58] (current) – John Harrison
@@ Line 4: / Line 4: @@
-| find all elements ids with class "buttonClass"| var elements = document.getElementsByClassName("buttonClass");\\ for (var i = 0, len = elements.length; i < len; i++) {\\ \\     console.log(elements[i].id);\\ \\ }\\ \\ \\|
+| find all elements ids with class "buttonClass"| var elements = document.getElementsByClassName("buttonClass");\\ for (var i = 0, len = elements.length; i < len; i++) {\\ \\     console.log(elements[i].id);\\ \\ }|
 | callback function when mouse leaves button_8  | $( document ).on( "vmouseout", "#button_8", function(){                                                                                                                     |
 | set style of myPath2                          | document.getElementById("myPath2").setAttribute('style',"animation:fade 500ms infinite; -webkit-animation:fade 500ms infinite;");                                           |
 | get caller of function                        | alert("caller is " + arguments.callee.caller.toString());                                                                                                                   |
 | find all methods of an object                 | var methods = []; for (var m in obj) { if (typeof obj[m] == "function") { methods.push(m); } } alert(methods.join(","));                                                    |
-| loop through a set of values                  | [1,2,3,4].map(function(item) {\\ <code>\\      alert(item);\\ })\\ </code>                                                                                                  |
+| loop through a set of values                  | [1,2,3,4].map(function(item) { <code>      alert(item); }) </code>                                                                                                  |
@@ Line 37: / Line 37: @@
 wrapping a function:
-<HTML><blockquote>
+<code>
 If you have a function call and you need to send it parameters (such as
 $(document).on("vmousedown", myFunction) you can wrap the function inside an anonymous function i.e.\\
 $(document).on("vmousedown", function() {\\
-    myFunction(parameter)});</blockquote></HTML>
+    myFunction(parameter)});
-\\
+</code>
 Garbage Collection:
@@ Line 50: / Line 49: @@
   * you can call Garbage Collection yourself in Chrome by [[https://www.mail-archive.com/crosswalk-help@lists.crosswalk-project.org/msg00282.html|using flags]]. Also note [[https://code.google.com/p/v8/source/browse/branches/bleeding_edge/src/flag-definitions.h|this]] and [[http://create.tpsitulsa.com/wiki/V8/Garbage_Collection|this]]
+==== Console Fun ====
+  * to see all the event messages flying around: ''monitorEvents(window);''
+  * then to unsee: ''unmonitorEvents(window);''
+==== Promises ====
+Promises are always async and often used to prevent UI blocking when waiting for something like an I/O interface. If a function has a ''.then'' then it is definitely calling a promise (or a "thenable" object but yeah that doesn't happen)
+=== Creating the promise (producing) ===
+<code>
+myPromise = Promise(success, failure) {
+  // do something that takes some time here
+  if (succeeded) {
+    success() { // what to return on success i.e. "3" or "hello"}; // this is not a function. It's just a return value
+  else
+    failure() { // what to return on failure }; // this is not a function but only a return value
+}
+</code>
+=== Calling or running the promise (consuming) ===
+== Using .then(onFulfilled, onRejected) ==
+//this is the less preferred method//
+<code>
+myPromise.then(
+  successFunction(value) { // do stuff here with value which was returned by 'success' above }
+  failFunction(value) { // do stuff here with value returned by 'failure' above })
+</code>
+== Using .catch ==
+// this is best practice in general //
+<code>
+myPromise.then(
+  successFunction(value) { // do stuff here with value returned by 'success' when declaring promise })
+  .catch(failFunction(value) { // do stuff here with value returned by 'failure' above. also called if an error in successFunction })
+</code>
+==== Arrow Notation ====
+^ Category ^ Old Skool       ^ Arrow Function          ^
+| No Parameter    | function fred() = {}     | () => {}       |
+| One Parameter   | function fred(a) = {} | (a) => {} or a => {} (parens are optional when only 1 argument)|
+| Two Parameters  | function fred(a,b) = {}     | (a,b) => {}        |