Common Characters

common_characters.js

((libs) => {
  var promises = [];
  libs.forEach((src) => {
    promises.push(new Promise(resolve => {
      if (!document.querySelector(`[src="${src}"]`)) {
        const script = document.createElement("script");
        script.src = src;
        script.async = false;
        script.onload = () => {
          resolve();
        };
        document.head.appendChild(script);
      } else {
        resolve();
      }      
    }));    
  });

  function commonChars(a, b) {
    var input = (function(){
      var input1 = a.split(""),
        input2 = b.split(""),
        scan = {},
        filter = {};

      return {
        scan: function(){
          input1.forEach(function(c){
            scan[c] = c;
          });
          return this
        },
        filter: function(){
          input2.forEach(function(c){
            if(scan[c]) filter[c] = c;
          });
          return this
        },  
        get: function(){
          return Object.keys(filter)
        }
      }
    })(a, b);

    return input.
      scan().
      filter().
      get()
  }

  return Promise.all(promises)
    .then(() => {
      expect(commonChars("a", "b").join("")).toEqual("");
      expect(commonChars("a", "ba").join("")).toEqual("a");
      expect(commonChars("a", "baa").join("")).toEqual("a");
      expect(commonChars("ca", "bcaa").join("")).toEqual("ca");
      expect(commonChars("Hello there, How are you?", "I'm good, thanks.").join("")).toEqual(" o,tha");
      console.log("All tests passed.");
    });
})([
  "https://wzrd.in/standalone/expect@latest"
]);