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Rooted by: Check Even Number
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  • Code 
    const isEven=i=>Number.isInteger(i)?!(i%2):undefined
     Preloaded Code 
                                                                                                                                                       _=n=>!(n%1)
    Test Cases 
    const expect = require("chai").expect;
describe("Solution", function() {
  it("should be true for 4", function() {
    expect(isEven(4)).to.equal(true);
  });
  it("should be false for 1", function() {
    expect(isEven(1)).to.equal(false);
  });
  it("should be undefined for 1.5", function() {
    expect(isEven(1.5)).to.equal(undefined);
  });
  it("should be undefined for NaN", function() {
    expect(isEven(NaN)).to.equal(undefined);
  });
  it("should be undefined for Infinity", function() {
    expect(isEven(Infinity)).to.equal(undefined);
  });
  it("should be undefined for -Infinity", function() {
    expect(isEven(NaN)).to.equal(undefined);
  });
  it("should be undefined for undefined", function() {
    expect(isEven(undefined)).to.equal(undefined);
  });
});
    View Run Output
  • Code
    • function isEven(input) {
    • if(!Number.isInteger(input)) {
    • return undefined
    • }
    • return input.toString(2).at(-1) == false
    • }
    • const isEven=i=>Number.isInteger(i)?!(i%2):undefined