JavaScript Interview Answers
- 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.
- 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);
- What is negative infinity?
It’s a number in JavaScript, derived by dividing negative number by zero.
- What does "1"+2+4 evaluate to?
Since 1 is a string, everything is a string, so the result is 124.
- 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.
- How do you create a new object in JavaScript?
var obj = new Object(); or var obj = {};
- What’s a way to append a value to an array?
arr[arr.length] = value;
- What are JavaScript types?
Number, String, Boolean, Function, Object, Null, Undefined.
- What does isNaN function do?
Return true if the argument is not a number.
- What boolean operators does JavaScript support?
&&, || and !
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Answers sourced from www.techinterviews.com
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