JavaScript Number Type Checker

JavaScript Number Type Checker Number.isInteger

JavaScript Number Type Checker

Number.isInteger

//  static 方法
Number.isInteger(value)

​

demo

function fits(x, y) {
  return Number.isInteger(y / x);
}

console.log(fits(5, 10));
// true

console.log(fits(5, 11));
// false

Number.isSafeInteger

The safe integers consist of all integers from -(2⁵³ - 1) inclusive to 2⁵³ - 1 inclusive (± 9007199254740991 or ± 9,007,199,254,740,991).

​​<sup>53</sup>​​ === 2^53

//  static 方法
Number.isSafeInteger(testValue)

​

function warn(x) {
  if (Number.isSafeInteger(x)) {
    return 'Precision safe.';
  }
  return 'Precision may be lost!';
}

console.log(warn(Math.pow(2, 53)));
// "Precision may be lost!"

console.log(warn(Math.pow(2, 53) - 1));
// "Precision safe."

Number.isNaN

value is NaN & type is Number

//  static 方法
Number.isNaN(value)

​

demo

function typeOfNaN(x) {
  if (Number.isNaN(x)) {
    return 'Number NaN';
  }
  if (isNaN(x)) {
   // string NaN?
    return 'NaN';
  }
}

console.log(typeOfNaN('100F'));
//  "NaN"

console.log(typeOfNaN(NaN));
// "Number NaN"

Number.isFinite

//  static 方法
Number.isFinite(value)