JavaScript to avoid pits

1, js arithmetic accuracy problem =

1 input >0.1+0.2==0.3 2 return >false 3 4 input >0.1+0.2 5 return >0.30000000000000004

Weapon: The  idea is very simple, first assigned to a variable, with tofixed (reserved decimal place), function rounding, but this is not enough, if the value of processing also need to participate in the operation, you need to use number (value/variable);

1 input >var num=0.1+0.2;　　2 input >var num2=num.tofixed (2);　　3 input >num2 4 return > "0.30" 5 input >number (num2); 6 Back to >0.3

2,JS variable operation problem

1 Input > "2"-3 2 return >-1 3 4 input > "2" +3 5 return > "23" 6 7 Input > "2" +-3 8 return > "2-3"

Turn all the operation parameters first into number type and then the operation, if it is a variable type, you need to pay attention to whether your variable contains numbers, if not included is more troublesome, need to use isNaN (variable);

1 input >number ("2")-number ("3") 2 return >-1 3 4 input >number ("2") +number ("3") 5 return >5 6 7 input >number ("2") +-numb ER ("3") 8 return >-1

3, numeric string comparison size problem   if the types of values on both sides are inconsistent, be sure to convert to a consistent type of variable comparison to be accurate (numeric and numeric string comparisons are also pits ...). )

1 input > "1" > "2" 2 return >false 3 4 input > "One" > "9" 5 return >false

JS in the true, false and undefined problem =

1 input >undefined==true 2 return >false 3 4 input >undefined==false 5 return >false 6 7 input >if (!undefined) Console.lo　　g (false); 8 Back to >false


It looks more weird, right? , I want to say is: this no solution ... (Let me cry for a moment ...)

)。。。 For this can only be memorized, a simple summary is: undefined this east is not equal to false is not equal to true, but, but, knocking on the blackboard = in the judgment statement it is false

JavaScript to avoid pits