javascript - instanceof contradicts the object type returned by typeof method -

here have array of number containing 6 elements.

var arr=[1.22,2.33,2.002,3.992,3.05,5.44]; 

then store each element inside variable , tried find out type of object is.i tried both typeof , instanceof .typeof saying variable used contain array value number instance of saying not number.so 1 correct..

then changed array little .used string values instead of number inside array..

var arr=["1.22","2.33","2.002","3.992","3.05","5.44"]; 

here typeof declaring values number type while instanceof saying opposite. can safe use typeof instead of instanceof .so question when use typeof , when use instanceof , how can avoid type of confusion??

code:

<script>     function init() {         var arr = ["1.22", "2.33", "2.002", "3.992", "3.05", "5.44"];         (i = 0; < arr.length; i++) {             var bag = arr[i];             alert(typeof bag == 'string');             alert(bag instanceof string);         }     }     window.onload = init; </script> 

typeof saying variable used contain array value number instance of saying not number.so 1 correct.

both. :-)

javascript has both primitive , object versions of numbers, strings, , booleans. typeof says "number" primitive numbers, not objects, , not instanceof number.

var = 5; console.log(typeof a);            // "number" console.log(a instanceof number); // false 

it's very rare you'll ever want explicitly create , keep reference object version of number, string, or boolean.

so why have them? can seem have methods on primitives. let's @ a variable above again, , add statement end:

var = 5; console.log(typeof a);            // "number" console.log(a instanceof number); // false console.log(a.tofixed(3);         // "5.000" 

huh? a refers primitive number. primitives don't have methods. how call tofixed method?

the answer javascript engine temporarily promotes primitive equivalent object type, uses object type's methods, , throws away object. (in theory; in practice, of course, engines optimize process.)

you can create number instance:

var = new number(5); console.log(typeof a);            // "object" console.log(a instanceof number); // true 

...but again, it's very, rare thing need do.