REACT Flashcards

1
Q

What is React?

A

JS Library for building User Interfaces

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2
Q

What is a React Element?

A

Object

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3
Q

How do you mount a react element to the DOM?

A

query the dom for the root

reactDOM.render(element, container, callback)

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4
Q

What is Babel?

A

Babel is a toolchain that is mainly used to convert ECMAScript 2015+ code into a backwards compatible version of JavaScript in current and older browsers or environments.

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5
Q

What is a Plug-In?

A

Software component that adds a specific feature to an existing computer program

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6
Q

What is a Webpack loader?

A

transformation s that are applied to the source code of a module. They allow you to pre-process files as you import and “load” them.

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7
Q

How can you make Babel and Webpack work together?

A

Install babel Loader

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8
Q

What is JSX?

A

Syntax extension of JavaScript, allows us to write HTML in react, makes it easier to write and add HTML in React. Provides a visual aid when working with UI inside the javascript code.

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9
Q

Why must the React object be imported when authoring JSX in a module?

A

JSX complies into calls to React.createElement, react library must always be in scope from your JSX code.

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10
Q

How can you make Webpack and Babel work together to convert JSX into valid JavaScript?

A

Use babel loader

Install babel/plugin-transform-react-jsx

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11
Q

What is a React Component?

A

Independent, reusable bits of code, serves the same purpose of Javascript functions, but works in isolation and returns HTML

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12
Q

How do you define a function component in React?

A

Function functionName(props){ return react element}

Class functionName extends React.Component {render() { return react element}}

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13
Q

How do you mount a component to the DOM?

A

Query the DOM for the root

Assign the component to a const variable, (
root.render(variableName)

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14
Q

What are props in React?

A

Properties in react and used for passing data from one component to another

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15
Q

How do you pass props to a component?

A

Prop.name

propertyName = {}
propertyName = 'string'
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16
Q

How do you write Javascript expressions in JSX?

A

Wrap them with curly braces

17
Q

How do you create “class” component in REACT?

A

class CLASSNAME extends React.Component {
render()
}

18
Q

How do you access props in a class component?

A

This object

19
Q

What is the purpose of state in React?

A

keep track of values that will change over time

20
Q

How to you pass an event handler to a React element?

A

As a prop , whatever event = {this.method}

21
Q

What are controlled components?

A

Input value controlled by React that renders a form and also controls what happens

22
Q

What two props must you pass to an input for it to be “controlled”?

A

Value and onChange

23
Q

What Array method is commonly used to create a list of React elements?

A

Map

24
Q

What is the best value to use as a “key” prop when rendering lists?

A

Use IDs from your data as keys, when you dont have stable IDs, you may use the item index as a key as a last resort.

25
Q

When does React call a component’s componentDidMount method?

A

After render, after react updates DOM and refs and before updating

26
Q

Name three React.Component lifecycle methods.

A

componentDidMount(), componentDidUpdate(), componentWillUnmount(), constructor(), render()

27
Q

How do you pass data to a child component?

A

props