.includes(value)Checks whether a string contains a given value.
JavaScript Methods
Fast lookup for commonly used JavaScript methods. This is a compact reference layer; full concepts, examples and lesson progression stay in the canonical BrounStack JavaScript tutorial.
String methods
.startsWith(value)Checks whether a string begins with a given value.
.endsWith(value)Checks whether a string ends with a given value.
.slice(start, end)Returns a selected portion of a string without changing the original.
.replace(search, value)Returns a string with a matched value replaced.
.split(separator)Splits a string into an array using a separator.
.trim()Removes whitespace from both ends of a string.
.toLowerCase() / .toUpperCase()Returns a lower-case or upper-case version of the string.
Array methods
.push(value)Adds one or more items to the end of an array and returns the new length.
.pop()Removes and returns the last item.
.shift() / .unshift()Removes the first item or adds items to the beginning.
.slice(start, end)Returns a shallow copy of a selected array portion.
.splice(start, count, ...items)Removes, replaces or inserts array items in place.
.map(callback)Creates a new array by transforming each item.
.filter(callback)Creates a new array containing items that pass a test.
.find(callback)Returns the first item that passes a test.
.some(callback) / .every(callback)Checks whether some or all items pass a test.
.reduce(callback, initial)Combines array items into a single accumulated result.
.includes(value)Checks whether an array contains a value.
.join(separator)Combines array items into a string.
Object methods
Object.keys(obj)Returns an array of an object's own enumerable property names.
Object.values(obj)Returns an array of an object's own enumerable property values.
Object.entries(obj)Returns key-value pairs as nested arrays.
Object.assign(target, ...sources)Copies enumerable own properties from source objects to a target.
Object.hasOwn(obj, key)Checks whether an object has a property as its own property.
Object.freeze(obj)Prevents adding, removing or changing properties at the top level.
Number & Math utilities
Number.isNaN(value)Checks whether a value is the numeric NaN value.
Number.isInteger(value)Checks whether a value is an integer.
Number.parseInt(value)Parses a string-like value and returns an integer when possible.
Math.round(value)Rounds to the nearest integer.
Math.floor(value) / Math.ceil(value)Rounds down or up to an integer.
Math.max(...values) / Math.min(...values)Returns the largest or smallest supplied numeric value.
JSON utilities
JSON.stringify(value)Converts a JavaScript value into a JSON string when supported.
JSON.parse(text)Parses valid JSON text into a JavaScript value.
Reference, not duplication: this page is for quick method lookup. Full JavaScript teaching, runnable examples and guided lessons remain in the existing BrounStack JavaScript tutorial.