Javascript

Create an regular expression object

Replace string 'aaa' by 'xyz'.

   1 var stringx = 'aaa bbb ccc';
   2 var regexx = new RegExp('aaa','g');
   3 stringx = stringx.replace( regexx , 'xyz' );

Delete property from object

   1 delete obj['propertyName'];

Number of milliseconds since epoch

   1 var nrmillis = Date.now();

Foreach in array

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

   1 function logArrayElements(element, index, array) {
   2     console.log("a[" + index + "] = " + element);
   3 }
   4 [2, 5, 9].forEach(logArrayElements);
   5 // logs:
   6 // a[0] = 2
   7 // a[1] = 5
   8 // a[2] = 9
   9

Context with this and bind

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.

   1 /*Constructor function*/
   2 function Counter(){     
   3   this.counter=0;
   4 }
   5 
   6 Counter.prototype.run=function(){
   7   console.log('counter:',this.counter);
   8   this.counter++;
   9   //recall run
  10   setTimeout(this.run.bind(this),1000);
  11 };
  12 
  13 var c = new Counter();
  14 setTimeout( c.run.bind(c) ,1000); // apply context of c to this
  15

arguments

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/arguments An Array-like object corresponding to the arguments passed to a function. You can refer to a function's arguments within the function by using the arguments object. This object contains an entry for each argument passed to the function, the first entry's index starting at 0.