🔰function expression

an expression that evaluates to a function object.

JS ⟩ value ⟩ function ⟩ expression

an expression that evaluates to a function as value.

//           ╭─── 🔸 function expression ───╮
const area = function (w, h) { return w * h };

different forms of F.E.
- arrow function
- IIFE
features of F.E.
roles of function expression：
- as variable ( 👉 more about：function expression as variable)
- as argument (also called a callback)
- as method

replit：function expression

//           ╭─── 🔸 function expression ───╮
const area = function (w, h) { return w * h };    // ⭐️ 1. as "variable"

const math = {                        // ⭐️ 2. as "method"
                                      // 🔸 "named" function expression
    //       ⤷╭──────────────╮ <-------- 🔸 function name: "f" (local)
    factorial: function f(n) {        //     available only in function body.
        // ...
    }
};

//  ╭── 🔸 FE ──╮
  ( function(){ } )();          // ⭐️ 3. as "IIFE" (form 1)

// ╭─── 🔸 FE ──╮
   !function(){ }();            // ⭐️ 3. as "IIFE" (form 2)

//          ╭─── 🔸 FE ────╮
f('click',  function (e) { } ); // ⭐️ 4. as "callback"

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Last updated 3 years ago