delete myArray[n] (faster, but leaves a gap at index n)
myArray.splice(n,1) (slower, but does not leave a gap in the array)
For example, to delete the myArray[5] element from myArray (leaving a gap), use the
delete statement: delete myArray[5]. You can use myArray.hasOwnProperty(n) to
check if the element myArray[n] is present in myArray. Note that setting the
array element to null or to undefined is not equivalent to deleting the element,
as shown in the example below:
var myArray = new Array(0,10,20,30,40);
// myArray[5] does not exist yet
document.write(myArray[5]); // undefined
document.write(typeof myArray[5]); // undefined
document.write(myArray.hasOwnProperty(5)); // false
// create myArray[5] by assignment
myArray[5] = 1; // 1
document.write(typeof myArray[5]); // number
document.write(myArray.hasOwnProperty(5)); // true
myArray[5] = null; // null
document.write(typeof myArray[5]); // object
document.write(myArray.hasOwnProperty(5)); // true
myArray[5] = undefined; // undefined
document.write(typeof myArray[5]); // undefined
document.write(myArray.hasOwnProperty(5)); // true
delete myArray[5];
document.write(myArray[5]); // undefined
document.write(typeof myArray[5]); // undefined
document.write(myArray.hasOwnProperty(5)); // false
Just like deleting an array element, you can also delete an object property. However,
in JavaScript you cannot delete a variable declared with the var keyword at the
time of first use.