js - pen questions collected

Get request parameter extraction

There is such a the URL of: http://item.taobao.com/item.htm?a=1&b=2&c=&d=xxx&e, please write a JS process to extract each GET parameters (parameter name and number of uncertainties) URL in , which is returned in the form of a key-value json structure, such as {a `: '. 1' , B: '2', C: '', D: 'XXX', E: undefined}`.

let str = 'http://item.taobao.com/item.html?a=1&b=2&c=&d=xxx&e&a=2'

function (str) {
  let params = {}
  const paramsStr = str.replace(/.*?/, '') 

  
  paramsStr.split('&').forEach(v => {
    d = v.split('=') // [a, 1] [b, 2] [c, ''] [d, xxx] [e]
    if (d[0] in params) {
      Array.isArray(params[d[0]]) ? params[d[0]].push(d[1]) : (params[d[0]] = [params[d[0]], d[1]])
    } else {
      params[d[0]] = d[1]
    }
  })
  return params
}

console.log(test(str)) // { a: [ '1', '2' ], b: '2', c: '', d: 'xxx', e: undefined }

Array dimensionality reduction

You can use Array.prototype.flat()es6 +

let arr = [[1, 2], [3, 4]]

the let newArr arr.flat = () // [. 1, 2,. 3,. 4] default dimension reduction layer

// 手写
let newArr2 = Array.prototype.concat.apply([], arr) // [1, 2, 3, 4]

js computing

const arr = [1, 8, 6, 2, 5, 4, 8, 3, 7]

function maxArea(arr) {
  let [start, area] = [0, 0]
  let end = arr.length - 1
  while (start < end) {
    const h = Math.min(arr[start], arr[end])
    const result = h * (end - start)
    area = result > area ? result : area
    arr[start] > arr[end] ? end-- : start++
  }
  return area
}
console.log(maxArea(arr)) // 49

返回 1 到 400 所有自然数中一共出现过多少次“1”，如 1 到 21 一共出现过 13 次“1”

let count = 0

for (let num = 1; num <= number; num++) {
  ;`${num}`.replace(/1/g, () => count++)
}

console.log(count) // 180

正则

给定字符串 str，检查其是否包含连续重复的字母（a-zA-Z），包含返回 true，否则返回 false

let str = 'adfdsaccsdd'
function containsRepeatingLetter(str) {
  return /([a-zA-Z])1/.test(str) // // 1指代第一个括号的匹配项
}

console.log(containsRepeatingLetter(str)) // true

字符串转驼峰

例如：border-bottom-color —-> borderBottomColor

let str = 'border-bottom-color'

function toHump(params) {
  let newStr = ''
  params.split('-').forEach((d, i) => {
    newStr += i === 0 ? d : `${d.charAt(0).toUpperCase()}${d.substring(1)}`
  })
  return newStr
}

console.log(toHump(str)) // borderBottomColor

Original: Big Box js - pen questions collected

js - pen questions collected

Get request parameter extraction

Array dimensionality reduction

js computing

正则

字符串转驼峰

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