JavaScript Test Solution

1. What’s relationship between JavaScript and ECMAScript? -
ECMAScript is yet another name for JavaScript (other names include LiveScript).
The current JavaScript that you see supported in browsers is ECMAScript revision 3.
2. What are JavaScript types? -
Number, String, Boolean, Function, Object, Null, Undefined.
3. How do you convert numbers between different bases in JavaScript? -
Use the parseInt() function, that takes a string as the first parameter, and the base as
a second parameter. So to convert hexadecimal 3F to decimal, use parseInt ("3F", 16);
4. What does isNaN function do? -
Return true if the argument is not a number.
5. What is negative infinity? -
It’s a number in JavaScript, derived by dividing negative number by zero.

6. What boolean operators does JavaScript support? -
&&, || and !
7. What does "1"+2+4 evaluate to? -
Since 1 is a string, everything is a string, so the result is 124.
8. How about 2+5+"8"? -
Since 2 and 5 are integers, this is number arithmetic, since 8 is a string, it’s concatenation,
so 78 is the result.
9. What looping structures are there in JavaScript? -
for, while, do-while loops, but no foreach.
10. How do you create a new object in JavaScript? -
var obj = new Object(); or var obj = {};
11. How do you assign object properties? -
obj["age"] = 17 or obj.age = 17.
12. What’s a way to append a value to an array? -
arr[arr.length] = value;
13. What is this keyword? -
It refers to the current object.