This
In JavaScript, the this value is determined by a function’s call context or, for an arrow function, inherited lexically.
Secrets of the JavaScript Ninja, Second Edition
The implicit JavaScript function binding whose value is determined by how the function is called.
- How it is used
- Determines which object function code accesses through `this`, especially in methods, constructors, and callbacks.
- How deep it goes
- Works through four invocation forms and callback remedies, while deferring detailed event handling.
- Examples
- Contrasts calls through two objects and traces a click handler that updates the wrong object.
- What you can do after
- Diagnose/debug with it when callbacks lose their intended context, then use `bind` or an appropriately placed arrow function.
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Essential TypeScript 5, Third Edition
The this value is the object or other value associated with a JavaScript function invocation or lexical function context.
- How it is used
- Controls which object’s properties methods and callbacks read, particularly when a function is detached or used as an event handler.
- How deep it goes
- Works through stand-alone calls, methods, call, bind, and enclosing arrow functions, then applies the behavior to a TSX handler.
- Examples
- Contrasts direct and detached message calls, repairs a price-display method with bind, and uses arrow handlers in a TSX product item.
- What you can do after
- Diagnose/debug with it when detached methods read unexpected properties, and choose bind or an enclosing arrow for consistent callback behavior.
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Build a Frontend Web Framework (From Scratch)
The JavaScript binding that determines the object supplied as the this value during a function call.
- How it is used
- Binds component render and event-handler callbacks to the component instance so state updates target the intended component.
- How deep it goes
- Explains callback binding, contrasts class methods, and implements explicit binding with call(), without surveying all JavaScript binding rules.
- Examples
- Uses a counter component, an increment button, and a parent handling a child’s emitted event.
- What you can do after
- Apply it via Function.call to preserve component context in render callbacks and event handlers.
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The Joy of JavaScript
this is a JavaScript binding whose value depends on the call site and refers to the current execution context or receiver.
- How it is used
- Uses this to access object state while decomposing a hashing method into smaller, composable functions.
- How deep it goes
- Explains context assumptions, dynamic binding, and explicit-parameter refactoring, but does not develop a complete call-site taxonomy.
- Examples
- Uses assemble, computeCipher, calculateHash, bind, and explicit object arguments in hashing examples.
- What you can do after
- Diagnoses hidden context dependencies and refactors this-based property access into explicit, composable functions.
Related concepts
- function bindingconfigured by · Function binding is the creation of a function with a predetermined this value and, optionally, preset arguments.
- callconfigured by · Function.prototype.call is a JavaScript method that invokes a function with a specified this value and arguments supplied individually.
- callconfigured by · A function call is an operation or expression that invokes a function or other callable, optionally supplies arguments, and initiates its execution.
- method invocationused by · A method invocation is an operation that calls a method or callable operation, optionally with a receiver and arguments, causing its behavior to execute.
- new keywordused by · In JavaScript, new is an operator that creates an object instance by invoking a constructable function or class as its constructor.
- applyconfigured by · Function.prototype.apply is a JavaScript method that invokes a function with a specified this value and arguments supplied as an array or array-like object.
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