China Dataset

The first line declares a data array and assigns the array content [1,2,3,4,' Message '], and then the second line declares the qq variable and adds the result of data.map(x=>x+1); , data.map(x=>x+1) is equivalent to data.map(function(x){return x+1});, so the first element of the array is enumerated for the first time after map starts enumerating. The value is 1, so return 1+1 will be executed, so the return array currently created by map is [2]. Next, the second value 2 of the array is listed, so return 2+1 will be executed, so the current return array created by map The return array is [2,3], and then the third value 3 of the array is listed, which will execute the return 3+1 program. It can be seen that the current return array created by map is [2,3,4].

The fourth enumeration of the fourth value 4 of the array will execute return 4+1. The current return array created by map is [2,3,4,5], and then the fifth value of the array is finally enumerated' new zealand whatsapp phone number Message 'So return ' Message '+1 will be executed , so the final return array created by map is [2,3,4,5,' Message '], and is passed back to the qq variable. The third line displays the current qq variable The value is [2,3,4,5,' Message ']. The fourth line declares a d2 array and assigns the array content [2,3,4,5,' nas ']. Next, the qq variable is changed to data .map(function(x,y,z){return z[y]+this[y]},d2). First, let’s introduce the parameter value z in the callback function as the data array, and y as the current array. List the position, the value of this is thisArg, so this is equal to d2.

Next, the first value enumerated by map is data[0], so y is equal to 0, so the return will be equal to data[0]+d2[0]=1+2, The current return array created by map is [3], and then the second value enumerated by map is data[1], so y is equal to 1, so the return array will be equal to data[1]+d2[1]=2+3, The current return array created by map is [3,5], and then map enumerates the third value as data[2], so y is equal to 2, so the return will be equal to data[2]+d2[2]=3+ 4. The current return array created by map is [3,5,7], and then map enumerates the fourth value as data[3], so y is equal to 3, so the return array will be equal to data[3]+d2[3 ]=4+5. The current return array created by map is [3,5,7,9]. Finally, the fifth value enumerated by map is data[4], so y is equal to 4, so the return array will be equal to data[ 4]+d2[4]=' Message '+' nas ', the final return array created by map is [3,5,7,9,' Messagenas '], [3,5,7,9,' Messagenas '] will be passed ba