Automation Service

12 June 2011

oDesk JavaScript Test Solution

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.

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