JavaScript Type Conversions

Transcript

1. JavaScript Type Conversions

2. JavaScript Primitives yes, js has primitives

3. 1. undefined 2. null 3. number 4. string 5. boolean

4. 1. undefined 2. null yep, is not an object 3.

   number 4. string 5. boolean

5. JavaScript Binary Operators we are going to address only -

   and +

6. On doubt check the spec

7. http://www.ecma-international.org/ecma-262/5.1/#sec-11.6.1 http://www.ecma-international.org/ecma-262/5.1/#sec-11.6.2

8. + Operator

9. If lprim or rprim are strings, then concatenate lprim and

   rprim and return the result

10. - Operator

11. ToNumber(lprim) - ToNumber(rprim)

12. Examples

13. var a, b; a = "bla"; b = "ble"; a

    + b; //=> "blable" a - b; //=> "NaN" a = "5"; b = "4"; a + b; //=> "54" a - b; //=> 1

14. var obj = { valueOf: function valueOf() { console.log("valueOf"); return

    {}; // not a primitive }, toString: function toString() { console.log("toString"); return {}; // not a primitive } }; obj - 1; // valueOf // toString // error obj + 1; // valueOf // toString // error

15. var func = function () { console.log('exec'); return { valueOf:

    function valueOf() { console.log("valueOf"); return {}; // not a primitive }, toString: function toString() { console.log("toString"); return {}; // not a primitive } }; }; func() + 1; // exec // valueOf // toString // error

16. {} + [] //=> +[] == 0 [] + {}

    //=> '' + '[object Object]' == '[object Object]' [] - {} //=> 0 - NaN == NaN {} - [] //=> -[] == -0
17. None

18. WAT https://www.destroyallsoftware.com/talks/wat