Javescript 0.1 + 0.2 = = 0.3 problem

According to the definition of double precision floating point number ,Number The valid integer range in type is -0x1fffffffffffff to 0x1fffffffffffff, therefore Number Can't represent integers outside this range exactly .

Again, according to the definition of floating point numbers , Non integer Number Type unavailable ==（=== Not good either. ） To compare , A famous piece of code , This is also the problem of our third question , Why is it JavaScript in ,0.1+0.2 You can't =0.3：

  console.log( 0.1 + 0.2 == 0.3);

The output here is false, Explain that the two sides are not equal , This is the characteristic of floating point operation , It is also the source of many students' doubts , The precision problem of floating-point operation leads to that the left and right results of the equation are not strictly equal , It's a tiny difference .

So actually , The wrong conclusion here is not , It's a method of comparison , The right way to compare is to use JavaScript The minimum accuracy value provided ：

  console.log( Math.abs(0.1 + 0.2 - 0.3) <= Number.EPSILON);

Check whether the absolute value of the difference between the left and right sides of the equation is less than the minimum accuracy , Is the right way to compare floating-point numbers . The result of this code is true 了 .