分享文章、钻研技术、改变生活！
Returns the last element in an array.
Check if arr is truthy and has a length property, use arr.length - 1 to compute the index of the last element of the given array and return it, otherwise return undefined.
继续阅读 30秒学会 JavaScript 片段 – last
站长
Returns the first key that satisfies the provided testing function. Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.prototype.find() to test the provided function for each key-value pair. The callback receives three arguments – the value, the key and the object.
继续阅读 30秒学会 JavaScript 片段 – findKey
站长
Changes a function that accepts an array into a variadic function.
Given a function, return a closure that collects all inputs into an array-accepting function.
继续阅读 30秒学会 JavaScript 片段 – collectInto.md
站长
Returns 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.
Calculate the ordering direction for the first two elements.
Use Object.entries() to loop over array objects and compare them in pairs.
Return 0 if the direction changes or the direction if the last element is reached.
继续阅读 30秒学会 JavaScript 片段 – isSorted
站长
Creates an array of arrays, ungrouping the elements in an array produced by zip.
Use Math.max.apply() to get the longest subarray in the array, Array.prototype.map() to make each element an array.
Use Array.prototype.reduce() and Array.prototype.forEach() to map grouped values to individual arrays.
继续阅读 30秒学会 JavaScript 片段 – unzip
站长
Creates a function that invokes the provided function with its arguments transformed.
Use Array.prototype.map() to apply transforms to args in combination with the spread operator (...) to pass the transformed arguments to fn.
继续阅读 30秒学会 JavaScript 片段 – overArgs
站长
Returns true if the given year is a leap year, false otherwise.
Use new Date(), setting the date to February 29th of the given year and use Date.prototype.getMonth() to check if the month is equal to 1.
继续阅读 30秒学会 JavaScript 片段 – isLeapYear
站长
Mutates the original array to insert the given values at the specified index.
Use Array.prototype.splice() with an appropriate index and a delete count of 0, spreading the given values to be inserted.
继续阅读 30秒学会 JavaScript 片段 – insertAt
站长
Runs a function in a separate thread by using a Web Worker, allowing long running functions to not block the UI.
Create a new Worker using a Blob object URL, the contents of which should be the stringified version of the supplied function.
Immediately post the return value of calling the function back.
Return a promise, listening for onmessage and onerror events and resolving the data posted back from the worker, or throwing an error.
继续阅读 30秒学会 JavaScript 片段 – runAsync
站长
Returns the maximum value of an array, after mapping each element to a value using the provided function.
Use Array.prototype.map() to map each element to the value returned by fn, Math.max() to get the maximum value.
继续阅读 30秒学会 JavaScript 片段 – maxBy
站长