Functions - Javascript

    function variable (parameters) {
        // Statements
        return value;
    }
    // Give parameter a default value
    function variable(parameters = value) {
        // Statements
    }
    // If only one argument & statement, Automatically return
    const variable = parameter => statement
    // Arrow Function
    const variable = (parameters) => {
        // Statements
    }
    const variable = function(parameters) {
        // Statements
    }
    variable(arguments) // Call a function

• Points to Object of the function it is inside of
• In case of arrow function it will find global window object if necessary or lexical this
• In case of events, it will refer to the element that receives the event

• Global
  • Available in every file loaded after it
• Module
  • Only available within that file unless you explicitly export it
• Function
  • var is available inside the whole function not just in block level
• Block
  • Available only inside the curly braces
  • let & const have block level scope
• Scope chain
  • Stack of currently accessible scopes, from the most immediate context to the global context

    (function () {
        // Statements
    })();
    variable(A).next().value

• A function has access to the variable environment (VE) of the execution context in which it was created
• Closure is VE attached to the function
• Code

      const functionName = function () {
          let varName1 = 0;
          return function () {
              varName1++;
          }
      }
      const varName2 = functionName();
      varName2();
  

• Code

      function functionName(A) {
          let var = 0;
          return {
              next: function () {
                  if (var < A.length) {
                      return {
                          value: A[var++], done: false
                      }
                  }
                  else {
                      return {
                          done: true
                      }
                  }
              }
          }
      }
      // Gives the next value of elements of array after each execution
      functionName(A).next().value
  

• Generator
  • The yield keyword pauses the generator function execution, and the value of the expression following the yield keyword is returned to the generator's caller, Returns a object with value & done just like Iterator
  • Code

        function* variable() {
            yield value1;
            yield value2;
        }
        variable(A).next().value // Gives the naxt value of elements of array after each execution