前言
大家好呀，我是毛小悠，能够叫我二毛，在家中排行老二，是一名前端开发工程师。
本系列文章旨在通过练习来进步JavaScript的能力，一起欢快的做题吧。
以下每道题，二毛我都有尝试做一遍。倡议限时训练，比方限定为半小时，如果半小时内想不进去，能够联合文章开端的参考答案来思考。
能够在下方评论区留言或者加我的微信：code\_maomao。期待你的到来。
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题目1：什么不属于这些？
编写一个办法，该办法承受一个元素数组并返回不属于这些元素的元素。
例：
[1, 2, 2, 2, 2] -> 1['1', 2, '4', '6', '8'] -> 2[2, 2, -2, 6, 10] -> -2['a', 'a', 'b', 'a', 'a', 'a', 'a'] -> 'b'元素只能是以下类型：
boolean，char（或在JS / TS中为一个字符的字符串）或int（在JS / TS中为数字）。
该数组永远不会为空，并且数组中始终会有两个以上的值！
它总是恰好是一个元素，不属于其余元素。
数组中的值永远不会为null或undefined或0。
习题代码：
function findTheNotFittingElement(series){ return null;}答案
题目1的答案
参考答案1：
function findTheNotFittingElement(series){ let arrOut = []; let arrChecks = [checkValue,checkType,checkEven,checkSign,checkStrVal,checkCase,checkAlphaNum] // Filter the array using various functions in arrChecks applied to the series. Looking for a single element to provide distinct response to filter. for(let j = 0; j < arrChecks.length; j++){ arrOut.push(series.filter(function(element,i){ if(i === 0){ return arrChecks[j](element) !== arrChecks[j](series[1]) && arrChecks[j](element) !== arrChecks[j](series[2]); } else if(i === 1){ return arrChecks[j](element) !== arrChecks[j](series[0]) && arrChecks[j](element) !== arrChecks[j](series[2]); } else { return arrChecks[j](element) !== arrChecks[j](series[i-2]) && arrChecks[j](element) !== arrChecks[j](series[i-1]); } })); } function checkValue(x){ return x; } function checkType(x){ return typeof x; } function checkEven(x){ return x%2; } function checkSign(x){ return x/Math.sqrt(x*x) } function checkStrVal(x){ return isNaN(x); } function checkCase(x){ return x.toString().match(/[a-z]+/); } function checkAlphaNum(x){ return x.toString().match(/[^a-z0-9]/i); } // Returning the first array where only one element is differentiated by a test filter. return arrOut[arrOut.findIndex(function(element){return element.length === 1})][0];}参考答案2：
function findTheNotFittingElement(s){ // |----->at least two type<-----| |--------->check out the unique type<---------| if(s.some(x=>typeof x!=typeof s[0])&&(t=check(x=>typeof x!=typeof s[0]))!="Failed!") return t // |-->only one value is not equals to s[0]<--| |--->search it out<---| if((t=s.filter(x=>x===s[0])).length==s.length-1) return s.filter(x=>x!=s[0])[0] // |-->only one value is not equals to s[1]<--| |--->search it out<---| if((t=s.filter(x=>x===s[1])).length==s.length-1) return s.filter(x=>x!=s[1])[0] // |----> even number <----| |----> odd number <----||---> negative <---||---> positive <--||-----> zero <----| |-----> string number <-----||-----> lowercase letter <-----||-----> uppercase letter <-----| |-----> is letter or not <-----||-----> execute each func <-----| tmp=[x=>typeof x=='number'&&x%2==0,x=>typeof x=='number'&&x%2==1,x=>Math.sign(x)==-1,x=>Math.sign(x)==1,x=>Math.sign(x)==0,x=>typeof x=='string'&&/\d/.test(x),x=>typeof x=='string'&&/[a-z]/.test(x),x=>typeof x=='string'&&/[A-Z]/.test(x),x=>typeof x=='string'&&/\w/.test(x)].some(f=>{if((t=check(f))!="Failed!") {r=t;return true}}) return r function check(f){ var t=s.filter(f) // |->unique found<-||---------> duplicate found <---------||->nothing found<-| return t.length==1?t[0]:t.length==s.length-1?s.filter(x=>!f(x))[0]: "Failed!" }}参考答案3：
function findTheNotFittingElement(series){ console.log(series) let len = series.length-1; let odd1 = [], odd2 = [], odd3 = [], odd4 = [], odd5 = [], odd6 = [], odd7 = [], odd8 = [], odd9 = [], odd10 = [], odd11 = [], odd12 = [], odd13 = [], odd14 = [], odd15 = [], odd16 = [], odd17 = [], odd18 = [], odd19 = [], odd20 = []; let ser = series.map((x,i) => x ); let serRev = series.reverse().map((x,i) => x );let difType = series.map((x,i) => typeof ser[i-1] == typeof x || typeof ser[i+1] == typeof x || typeof ser[i+2] == typeof x || typeof ser[i-2] == typeof x ? "" : odd2.push(i) ) let bool = series.map((x,i) => Boolean(x) == Boolean(ser[i-1]) || Boolean(x) == Boolean(ser[i+1]) ? " " : odd3.push(i)) let alpNum = series.map((x,i) => /[a-z]/gi.test(x) == true ? '' : odd4.push(i) )let difTypeRev = series.reverse().map((x,i) => typeof serRev[i-1] == typeof x || typeof serRev[i+1] == typeof x || typeof serRev[i-2] == typeof x || typeof serRev[i+2] == typeof x ? "" : odd5.push(i) )let boolRev = series.reverse().map((x,i) => Boolean(x) == Boolean(serRev[i-1]) || Boolean(x) == Boolean(serRev[i+1]) ? " " : odd6.push(i))let neg = series.map((x,i) => Math.sign(x) == -1 ? odd7.push(i) : odd8.push(i) ) let evenNum = series.map((x,i) => typeof x == 'number' && x % 2 == 0 ? odd9.push(i) : typeof x == 'number' && x % 2 != 0 ? odd10.push(i) : '' ) let capA = series.map((x,i) => /[a-z]/.test(x) == true ? odd11.push(i) : /[A-Z]/.test(x) == true ? odd12.push(i) : '' )let oneDifStrAlt = series.map((x,i) => x == ser[i-1] || x == ser[i+1] || x == ser[i-2] || x == ser[i+2] ? odd13.push(i) : '') let noDup = series.map((x,i) => typeof x == 'string' && series.indexOf(x) ? odd15.push(i): typeof x == 'string' && !series.indexOf(x)?odd16.push(i):'') let numOnly = series.map((x,i) => typeof x == 'number' && x === ser[i-1] || typeof x == 'number' && x === ser[i+1] ? odd17.push(i) : '') let tr = []; let fa = [];let trueFalse = series.map((x,i) => x == false ? fa.push(i) : x == true ? tr.push(i) : '')let ma = []; let mi = []; let maxMin = series.map((x,i) => {if (x == Math.max(...ser)) ma.push(i) if (x == Math.min(...ser)) mi.push(i)}) if (odd1.length == 1) {return series[odd1[0]]}if (odd2.length == 1) {return series[odd2[0]]} if (odd3.length == 1) {return series[odd3[0]]}if (odd4.length == 1) {return series[odd4[0]]} if (odd5.length == 1) {return series[odd5[0]]} if (odd7.length == 1) {return series[odd7[0]]} if (odd8.length == 1) {return series[odd8[0]]}if (odd9.length == 1) {return series[odd9[0]]} if (odd10.length == 1) {return series[odd10[0]]}if (odd11.length == 1) {return series[odd11[0]]} if (odd12.length == 1) {return series[odd12[0]]} if (odd14.length == 1) {return series[odd14[0]]} if (odd15.length == 1) {return series[odd15[0]]} if (odd16.length == 1) {return series[odd16[0]]} if (odd17.length == 1) {return series[odd17[0]]} if (odd18.length == 1) {return series[odd18[0]]} if (odd19.length == 1) {return series[odd19[0]]} if (odd20.length == 1) {return series[odd20[0]]} if (tr.length == 1) {return series[tr[0]]} if (fa.length ==1 ) {return series[fa[0]]} if (ma.length == 1) {return series[ma[0]]} if (mi.length == 1) {return series[mi[0]]} }参考答案4：
const findTheNotFittingElement = series => { let result, oddOne, iUnique = 0; // check typeOfCheck; const typeOfCheck = series.map(x => typeof x).reduce((acc, curr) => (acc[curr] ? acc[curr]++ : acc[curr] = 1, acc), {}); // acc as in = 1, acc is the same as return acc; // console.log(typeOfCheck); for (const [key, value] of Object.entries(typeOfCheck)) { if (value === 1) oddOne = key; } result = series.filter(x => typeof x === oddOne); if (result.length > 0) return result[0]; // check oddOneOut; const oddOneOut = series.reduce((acc, curr) => (acc[curr] ? acc[curr]++ : acc[curr] = 1, acc), {}); for (const [key, value] of Object.entries(oddOneOut)) { if (value === 1) oddOne = key, iUnique++; } if (iUnique === 1) { if (/false/.test(oddOne)) return false; if (/true/.test(oddOne)) return true; if (/\d/.test(oddOne)) return +oddOne; return oddOne; }; // check odd; if (series.every(i => typeof i === 'number' && i > 0)) return series.filter(x => x % 2)[0]; // check negative or positive; if (series.filter(i => typeof i === 'number' && i >= 0).length > series.filter(i => typeof i === 'number' && i < 0).length) { return series.filter(i => typeof i === 'number' && i < 0)[0]; } else if (series.filter(i => typeof i === 'number' && i >= 0).length < series.filter(i => typeof i === 'number' && i < 0).length) { return series.filter(i => typeof i === 'number' && i >= 0)[0]; } // check strings; const sLength = series.length; const caps = (series.join('').match(/[A-Z]/g) || [] ); const nonCaps = (series.join('').match(/[^A-Z]/g) || []); const lows = (series.join('').match(/[a-z]/g) || []); const nonLows = (series.join('').match(/[^a-z]/g) || []); const digits = (series.join('').match(/\d/g) || []); const nonDigits = (series.join('').match(/[^\d]/g) || []); const dots = (series.join('').match(/\W/g) || []); const nonDots = (series.join('').match(/[^\W]/g) || []); if (sLength - caps.length === 1) return nonCaps[0]; if (sLength - lows.length === 1) return nonLows[0]; if (sLength - digits.length === 1) return nonDigits[0]; if (sLength - dots.length === 1) return nonDots[0]; if (digits.length === 1 && lows.length === 1) return digits[0] if (dots.length === 1) return dots[0]}参考答案5：
function findTheNotFittingElement(series){console.log(`series=(${series.join(",")})`); if(!series || series.length<3) { return null; } const values = new Map(); const types = new Map(); const numbers = new Map(); const cases = new Map(); const alphas = new Map(); const evens = new Map(); const signs = new Map(); for(let i=0; i<series.length; i++) { let arr; const v = series[i]; arr = values.get(v) || []; arr.push(v); values.set(v, arr); const type = typeof v; arr = types.get(type) || []; arr.push(v); types.set(type, arr); let isEven=false; let isNumber=false; let isNegative=false; const n = Number.parseInt(v); if(n!==NaN) { isNumber=true; if(n % 2 === 0) { isEven=true; } arr = evens.get(isEven) || []; arr.push(v); evens.set(isEven, arr); if(n<0) { isNegative=true; } arr = signs.get(isNegative) || []; arr.push(v); signs.set(isNegative, arr); } arr = numbers.get(isNumber) || []; arr.push(v); numbers.set(isNumber, arr); let isAlpha=false; let cse; if( v>='a' && v<='z' ) { cse='low'; } if( v>='A' && v<='Z' ) { cse='high'; } if(cse!==undefined) { arr = cases.get(cse) || []; arr.push(v); cases.set(cse, arr); isAlpha = true; } arr = alphas.get(isAlpha) || []; arr.push(v); alphas.set(isAlpha, arr); } for(let [a,b] of [ ["types",types], ["numbers", numbers], ["alphas",alphas], ["cases",cases], ["evens",evens], ["signs",signs], ["values",values] ]) { console.log(a); console.dir(b); vv = checkMap(b); if(vv!==undefined) { return vv; } } return undefined;}function checkMap(map) { const keys = [...map.keys()]; if(keys.length===2) { const [type1, type2] = keys; console.log("type1,type2 = ",type1, type2); const arr1 = map.get(type1); const arr2 = map.get(type2);console.log(`arr1= ( ${arr1.join(",")} ) arr2=(${arr2.join(",")})`); if(arr1.length===1) { return arr1[0]; } if(arr2.length===1) { return arr2[0]; } } return undefined;}后序
本系列会定期更新的，题目会由浅到深的逐步提高。
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