Sun River
          Topics about Java SE, Servlet/JSP, JDBC, MultiThread, UML, Design Pattern, CSS, JavaScript, Maven, JBoss, Tomcat, ...
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           What are JavaScript types? - Number, String, Boolean, Function, Object, Null, Undefined.

          1. 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);
          2. What does isNaN function do? - Return true if the argument is not a number.
          3. What is negative infinity? - It’s a number in JavaScript, derived by dividing negative number by zero.

          4. What boolean operators does JavaScript support? - &&, || and !
          5. What does "1"+2+4 evaluate to? - Since 1 is a string, everything is a string, so the result is 124.
          6. 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.
          7. What looping structures are there in JavaScript? - for, while, do-while loops, but no foreach.
          8. How do you create a new object in JavaScript? - var obj = new Object(); or var obj = {};
          9. How do you assign object properties? - obj["age"] = 17 or obj.age = 17.
          10. What’s a way to append a value to an array? - arr[arr.length] = value;
          11. What is this keyword? - It refers to the current object.
          posted on 2009-03-10 11:37 Sun River 閱讀(278) 評論(0)  編輯  收藏
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