Classes and Methods

Method Chains

Create an instance and use its method result immediately.

method-chain For short-lived objects, creating an instance and using its method result in the next expression keeps the code compact while still showing the class behavior.

Method Chains

text
method_chain.js
Replay: real traced execution (multi-file project)
const text = "trace";
class TextTool {
  constructor(text) {
    this.text = text;
  }

  upper() {
    return this.text.toUpperCase();
  }
}

const output = new TextTool(text).upper();

console.log("text=" + text);
console.log("output=" + output);

const text = "replay";
class TextTool {
  constructor(text) {
    this.text = text;
  }

  upper() {
    return this.text.toUpperCase();
  }
}

const output = new TextTool(text).upper();

console.log("text=" + text);
console.log("output=" + output);

const text = "class";
class TextTool {
  constructor(text) {
    this.text = text;
  }

  upper() {
    return this.text.toUpperCase();
  }
}

const output = new TextTool(text).upper();

console.log("text=" + text);
console.log("output=" + output);

  1. text ← trace, this.text ← trace

    1const text→ trace = "trace"; //@text="replay", "class"2class TextTool {3  constructor(text) {4    this.text = texttrace;5  }67  upper() {8    return this.text.toUpperCase();9  }10}1112const output = new TextTool(texttrace).upper();
    values this steptracethis.text

  2. upper()

    4  this.text = text;5}67upper() {8  return this.texttrace.toUpperCase();9}

  3. output ← TRACE

    9  }10}1112const output→ TRACE = new TextTool(texttrace).upper();1314console.log("text=" + texttrace);15console.log("output=" + outputTRACE);
    outputtext=trace
output=TRACE

  1. text ← replay, this.text ← replay

    1const text→ replay = "replay";2class TextTool {3  constructor(text) {4    this.text = textreplay;5  }67  upper() {8    return this.text.toUpperCase();9  }10}1112const output = new TextTool(textreplay).upper();
    values this stepreplaythis.text

  2. upper()

    4  this.text = text;5}67upper() {8  return this.textreplay.toUpperCase();9}

  3. output ← REPLAY

    9  }10}1112const output→ REPLAY = new TextTool(textreplay).upper();1314console.log("text=" + textreplay);15console.log("output=" + outputREPLAY);
    outputtext=replay
output=REPLAY

  1. text ← class, this.text ← class

    1const text→ class = "class";2class TextTool {3  constructor(text) {4    this.text = textclass;5  }67  upper() {8    return this.text.toUpperCase();9  }10}1112const output = new TextTool(textclass).upper();
    values this stepclassthis.text

  2. upper()

    4  this.text = text;5}67upper() {8  return this.textclass.toUpperCase();9}

  3. output ← CLASS

    9  }10}1112const output→ CLASS = new TextTool(textclass).upper();1314console.log("text=" + textclass);15console.log("output=" + outputCLASS);
    outputtext=class
output=CLASS