feat: add functions code

sohamsshah · sohamsshah · commit 6aa3bbec1b6a · 2022-05-27T15:53:02.000+05:30
diff --git a/Snippets/Functions/bind.js b/Snippets/Functions/bind.js
@@ -0,0 +1,21 @@
+let user = {
+  firstName: "John",
+  sayHi() {
+    alert(`Hello, ${this.firstName}!`);
+  },
+};
+
+let sayHi = user.sayHi.bind(user); // (*)
+
+// can run it without an object
+sayHi(); // Hello, John!
+
+setTimeout(sayHi, 1000); // Hello, John!
+
+// even if the value of user changes within 1 second
+// sayHi uses the pre-bound value which is reference to the old user object
+user = {
+  sayHi() {
+    alert("Another user in setTimeout!");
+  },
+};
diff --git a/Snippets/Functions/bindAll.js b/Snippets/Functions/bindAll.js
@@ -0,0 +1,19 @@
+// If an object has many methods and we plan to actively pass it around, then we could bind them all in a loop
+
+const user = {
+  func1() {
+    console.log("func 1");
+  },
+  func2() {
+    console.log("func 2");
+  },
+  func3() {
+    console.log("func 3");
+  },
+};
+
+for (let key in user) {
+  if (typeof user[key] == "function") {
+    user[key] = user[key].bind(user);
+  }
+}
diff --git a/Snippets/Functions/boundFunctionMethod.js b/Snippets/Functions/boundFunctionMethod.js
@@ -0,0 +1,11 @@
+"use strict";
+function f() {
+  console.log(this); // null
+}
+
+let user = {
+  g: f.bind(null),
+};
+
+// f();
+user.g();
diff --git a/Snippets/Functions/fixFunctionThis.js b/Snippets/Functions/fixFunctionThis.js
@@ -0,0 +1,19 @@
+function askPassword(ok, fail) {
+  let password = "rockstar";
+  if (password == "rockstar") ok();
+  else fail();
+}
+
+let user = {
+  name: "John",
+
+  loginOk() {
+    console.log(`${this.name} logged in`);
+  },
+
+  loginFail() {
+    console.log(`${this.name} failed to log in`);
+  },
+};
+
+askPassword(user.loginOk.bind(user), user.loginFail.bind(user));
diff --git a/Snippets/Functions/globalPartialFunctions.js b/Snippets/Functions/globalPartialFunctions.js
@@ -0,0 +1,22 @@
+function partial(func, ...argsBound) {
+  return function (...args) {
+    // (*)
+    return func.call(this, ...argsBound, ...args);
+  };
+}
+
+// Usage:
+let user = {
+  firstName: "John",
+  say(time, phrase) {
+    alert(`[${time}] ${this.firstName}: ${phrase}!`);
+  },
+};
+
+// add a partial method with fixed time
+user.sayNow = partial(
+  user.say,
+  new Date().getHours() + ":" + new Date().getMinutes()
+);
+
+user.sayNow("Hello");
diff --git a/Snippets/Functions/partialFunctions.js b/Snippets/Functions/partialFunctions.js
@@ -0,0 +1,22 @@
+function mul(a, b) {
+  return a * b;
+}
+
+const triple = mul.bind(null, 3); // alternative to this is to curry functions
+
+console.log(triple(4));
+
+const user = {
+  firstName: "Samyak Shah",
+};
+function send(from, text, to) {
+  return `
+    By: ${from}
+    To: ${to}
+    Message:
+    ${text}, ${this.firstName}`;
+}
+
+const sendTo = send.bind(user, "soham@invact.com");
+
+console.log(sendTo("Hello World", "samyak@neog.com"));
diff --git a/Snippets/Functions/partialLogin.js b/Snippets/Functions/partialLogin.js
@@ -0,0 +1,15 @@
+function askPassword(ok, fail) {
+  let password = prompt("Password?", "");
+  if (password == "rockstar") ok();
+  else fail();
+}
+
+let user = {
+  name: "John",
+
+  login(result) {
+    alert(this.name + (result ? " logged in" : " failed to log in"));
+  },
+};
+
+askPassword(user.login.bind(user, true), user.login.bind(user, false)); // ?
diff --git a/Snippets/Functions/secondBind.js b/Snippets/Functions/secondBind.js
@@ -0,0 +1,10 @@
+// A function cannot be re-bound
+function f() {
+  console.log(this.name);
+}
+
+f = f.bind({ name: "John" });
+z = f.bind({ name: "Ann" });
+
+f(); // John
+z(); // John
