Java Script Interview Questions and Answers
Question - 81 : - How to set the cursor to wait ?
Answer - 81 : - In theory, we should cache the current state of the cursor and then put it back to its original state.
document.body.style.cursor = 'wait';
//do something interesting and time consuming
document.body.style.cursor = 'auto';
Question - 82 : - How to reload the current page ?
Answer - 82 : - window.location.reload(true);
Question - 83 : - how to force a page to go to another page using JavaScript ?
Answer - 83 : -
Question - 84 : - How to convert a string to a number using JavaScript?
Answer - 84 : - You can use the parseInt() and parseFloat() methods. Notice that extra letters following a valid number are ignored, which is kinda wierd but convenient at times.
parseInt("100") ==> 100
parseFloat("98.6") ==> 98.6
parseFloat("98.6 is a common temperature.") ==> 98.6
parseInt("aa") ==> Nan //Not a Number
parseInt("aa",16) ==> 170 //you can supply a radix or base
Question - 85 : - How to convert numbers to strings using JavaScript?
Answer - 85 : - You can prepend the number with an empty string
var mystring = ""+myinteger;
or
var mystring = myinteger.toString();
You can specify a base for the conversion,
var myinteger = 14;
var mystring = myinteger.toString(16);
mystring will be "e".
Question - 86 : - How to test for bad numbers using JavaScript?
Answer - 86 : - the global method, "isNaN()" can tell if a number has gone bad.
var temperature = parseFloat(myTemperatureWidget.value);
if(!isNaN(temperature)) {
alert("Please enter a valid temperature.");
}
Question - 87 : - What's Math Constants and Functions using JavaScript?
Answer - 87 : - The Math object contains useful constants such as Math.PI, Math.E
Math also has a zillion helpful functions.
Math.abs(value); //absolute value
Math.max(value1, value2); //find the largest
Math.random() //generate a decimal number between 0 and 1
Math.floor(Math.random()*101) //generate a decimal number between 0 and 100
Question - 88 : - What's the Date object using JavaScript?
Answer - 88 : - Time inside a date object is stored as milliseconds since Jan 1, 1970.
new Date(06,01,02) // produces "Fri Feb 02 1906 00:00:00 GMT-0600 (Central Standard Time)"
new Date(06,01,02).toLocaleString() // produces "Friday, February 02, 1906 00:00:00"
new Date(06,01,02) - new Date(06,01,01) // produces "86400000"
Question - 89 : - What does the delete operator do?
Answer - 89 : - The delete operator is used to delete all the variables and objects used in the program ,but it does not delete variables declared with var keyword.
Question - 90 : - How tp create Arrays using JavaScript ?
Answer - 90 : -
This produces
first day is Sunday
A more compact way of creating an array is the literal notation:
This produces
first day is Sunday