Write down some written test questions

One is known by ASCLL A string of characters , Find the first repeated character

Ideas ： Each element is compared with the following elements , Exit as long as they are equal , The first repeated character has been found .

function getFirstSameStr (string) {
    
    var i = 0
    for (i; i < string.length; i++) {
    
        for (var j = i + 1; j < string.length; j++) {
    
            if (string[i] == string[j]) {
    
                console.log(' The first repeated character is ', string[i])
                return
            } else {
    
                continue
            }
        }
    }
    console.log(' The string has no duplicate characters ')
}

Given an array , Array elements can only be numbers ,null,undefined,NaN. Find the maximum length of the array without repetition .

for example ： Input [1,4,3,4,null,undefined,NaN,null] Output 6
Ideas ： Turn every element into a string , Avoided null and undefined Influence .null == undefined by true,null === undefined by false, Each element is compared with the following elements , See if there is any repetition , Find the duplicate and delete the following .

function maxSonArray (array) {
    
    var i = 0
    for (i; i < array.length; i++) {
    
        //  All converted strings are easy to compare (null == undefined by true,null === undefined by false)
        array[i] = '' + array[i]
    }
    // console.log(' Processed array ', array)
    var sonArray = array
    i = 0
    for (i; i < sonArray.length; i++) {
    
        for (var j = i + 1; j < sonArray.length; j++) {
    
            if (sonArray[i] === sonArray[j]) {
    
                //  If you find a duplicate, get rid of it 
                sonArray.splice(j, 1)
            } else {
    
                continue
            }
        }
    }
    console.log(' Maximum subarray length ', sonArray.length, ' The largest subarray is ', sonArray)
}

Complete the function transform(url){ } Realization url Dynamic replacement of address parameters

for example let href=‘https://www.baidu.com/s?user=teml2&&wd=teml’
console.log(transform（href）({user:‘123’,wd:‘aa’,qq:‘321’}))
Output ：https://www.baidu.com/s?user=123&&wd=aa
Ideas ： First find ?,? And that's followed by the parameters , Parameter use && link , We will use && Split into arrays ,= The left and right sides are key value pairs , The direct use = Split key value pairs into arrays , Replace the old parameter value with the new one , Please note that the original parameters should be used instead of the new ones . So we iterate over the original parameters key To receive new parameter values , New fields are not needed . Finally, reassemble the string .

function transform (url, param) {
    
    //  find ? This is followed by the parameter string 
    var paramsindex = url.indexOf('?')
    //  Intercept ? The preceding string 
    var urlHead = url.substr(0, paramsindex + 1)
    //  Intercept ? String after 
    var paramsStr = url.substr(paramsindex + 1)
    //  Set the parameter string as '&&' Division 
    var paramsArray = paramsStr.split('&&')
    //  Change the parameter array into a key value pair and put it into the object 
    var keyValObject = {
    }
    paramsArray.forEach((element) => {
    
        let temp = element.split('=')
        keyValObject[temp[0]] = temp[1]
    });
    //  Merge parameter objects 
    let tempKeyArray = Object.keys(keyValObject)
    tempKeyArray.forEach((element) => {
    
        keyValObject[element] = param[element]
    })

    //  To add all the parameters of the new object, you can use the next line of code 
    // Object.assign(keyValObject, param)

    //  Regroup into url
    let target = ''
    let temparray = Object.entries(keyValObject)
    for (let i = 0; i < temparray.length; i++) {
    
        temparray[i] = temparray[i].join('=')
    }
    let parambody = temparray.join('&&')
    target = urlHead + parambody
    console.log(target)
}