commonErrors.txt

Source: https://flaviocopes.com/javascript-automatic-semicolon-insertion/

The rules of JavaScript Automatic Semicolon Insertion

The JavaScript parser will automatically add a semicolon when, during the parsing of the source code, it finds these particular situations:

    when the next line starts with code that breaks the current one (code can spawn on multiple lines)
    when the next line starts with a }, closing the current block
    when the end of the source code file is reached
    when there is a return statement on its own line
    when there is a break statement on its own line
    when there is a throw statement on its own line
    when there is a continue statement on its own line

Examples of code that does not do what you think

Based on those rules, here are some examples.

Take this:

const hey = 'hey'
const you = 'hey'
const heyYou = hey + ' ' + you

['h', 'e', 'y'].forEach((letter) => console.log(letter))

You’ll get the error Uncaught TypeError: Cannot read property 'forEach' of undefined because based on rule 1 JavaScript tries to interpret the code as

const hey = 'hey';
const you = 'hey';
const heyYou = hey + ' ' + you['h', 'e', 'y'].forEach((letter) => console.log(letter))