I want to know what will alert this javascript expression
alert( 20e-1['toString'](2) );
and I need detailed explanations about the answer.
Thank You for detailed answer!
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1Why don't you try it? – Jordan Running Nov 21 '15 at 19:37
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1try here http://jsfiddle.net/ – Md Ashaduzzaman Nov 21 '15 at 19:43
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20e-1 = 2 (mathematical operation). It is of a type "number" which is also an Object in javascript. Thus, we can write 2.someMethod(); Here, you call the toString() method, with brackets notation (and not dot notation) : 20e-1['toString'], which returns a litteral expression. Finally, you call the method with parenthesis, and add a parameter 2 to the method, which is the basis of the result, here a binary result. So... We have a 2 converted into a binary number => 10 which is expressed as a string '10'. – Arpp Nov 21 '15 at 19:49
1 Answers
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The result will be 10.
Let's dissect the expression 20e-1['toString'](2):
20e-1is a floating point number specified in scientific notation, which is a shorthand for20 * 10^-1 ( = 20 * 0.1 = 2).toStringis a property of a primitive value, the floating point number2.toStringis a function that converts the number to its string representation. The syntax suggests that the primitive value is promoted into aNumberobject whose propertytoStringis then referenced ( the reality is more complex,and this SO answer will explain it in much better informed way than I could repeat).(2)is the list of actual parameters to the methodtoString. The single parameter specifies a conversion of the number to the string representation in base 2.2in base 2 representtaion happens to be10which explains the output.
