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for (key in obj)
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Iterates over keys
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for (value of obj)
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Iterates over values
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arr.forEach(function(val, I, arr))
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Executes a function for each value.
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arr.every(function(val, i, arr))
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Returns true if every value passes the function test
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arr.reverse()
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Reverses the original array
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Searching
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arr.includes(val)
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Returns true if array contains a value
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arr.indexOf(val)
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Returns the index of a value in an array or -1 if not found
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arr.find(function)
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Returns the value of the first index to satisfy the function
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arr.findIndex(function)
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Returns the index of the first value to satisfy the function
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Add Values
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arr.splice(start, 0, items...)
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Adds items to array beginning at starting index
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arr.unshift(val)
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Adds val to front of array
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arr.push(val)
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Adds val to back of array
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Delete Values
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arr.splice(start, n)
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Delete n items from array beginning at starting index
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arr.shift()
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Removes arr[0] and returns the value
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arr.pop()
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Removes last value in a array and returns it
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Copy Values
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arr.slice(beg, end)
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Returns a shallow copy of arr from beg to end (non-inclusive)
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To String
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arr.join(separator)
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Returns a string from the array values, with an optional separator string
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JSON.stringify(arr)
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Returns a JSON string representation of array. Deep string.
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arr.toString()
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Returns a comma-delimited string of scalar array values. Shallow string.
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Sorting
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arr.sort()
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Sorts lexicographically
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arr.sort((a, b) => a - b)
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Sorts numbers
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num.toFixed(n)
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Returns a number rounded to n significant figures after the decimal
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num.toPrecision(n)
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Returns a string rounded to n significant figures
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num.toString()
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Returns a string representation of a number
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Object to Array
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Object.keys(obj)
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Array of obj keys
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Object.values(obj)
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Array of obj values
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Object.entries(obj)
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2D array of key:value pairs
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Object to String
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JSON.stringify(obj)
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obj to string
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JSON.parse(obj)
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string to obj
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Add/Remove Properties
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delete obj[key]
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Delete property
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obj[key] = value
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Add property
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str.slice(beg, end)
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returns a substring from beginning to end index
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str.toLowerCase()
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Returns a lowercase version of str
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String to Array
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str.split(separator)
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Returns an array of the string, split by the separator
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Searching Strings
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str.includes(str)
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Returns true if str is in string
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str.indexOf(str)
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Returns index of str if within string, or -1 otherwise
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str.startsWith(str, beg)
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Returns true if string starts with str, optionally from beg index.
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str.endsWith(str, len)
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Returns true if string starts with str, optionally limited to the first len characters
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Combine Strings
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str.concat(strings...)
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Returns new string concatenation
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Math.abs(num)
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Returns the absolute value of num
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Random Numbers
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Math.round(Math.random() * (max - min)) + min)
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Returns a random number between two ints
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Math.random()
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Returns a random number between 0 and 1.
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Rounding
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Math.floor(num)
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Goes down to the nearest int <= num
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Math.ceil(num)
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Goes up to the nearest int >= num
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Math.round(num)
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Rounds to the nearest int
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
