从 javascript 中的 arrays 数组中加入和拆分元素

Question

So I am learning JavaScript slowly but surely, can someone help me figure out the most efficient way of using join() and split() for very large array or arrays? Im talking thousands or lines from a spreadsheet... This is what I have so far.

 function joinsplitPaste () { var data = [["mike",33,,"KS","male"],["jan",32," ","KS","female"],["dave",33,,"KS","male"],["mike",33, ,"KS","male"],["stan",31,,"KS","male"],["beth",19,"dataText","KS","female"]]; var dataJoin = []; //sample is made up for (i = 0;i<data.length;i++) { return data[i].join(" "); dataJoin.push(data[i]); } var dataSplit = []; /* output - [["mike 33 "KS" "male"],["jan" 32 " " "KS" "female"],["dave" 33 "KS" "male"], and so on...*/ for (i = 0;i<data.length;i++) { return dataJoin[i].Split(" "); dataSplit.push(dataJoin[i]); } //hopefully dataSplit == data? }

Any suggestions would be appreciated, Thank you.

Answer 1

based on the last comment in your sample code, I am assuming the endgoal you are after is that 'dataSplit' array should be equal to original 'data' array.

However, there are 2 problems with the sample code due to which you can not achieve what you wish:

1. presence of 'return' statement inside 'for' loop: which stops execution of first loop just after first iteration and prevents second loop from even getting started.

2. equality check doesn't work for non-primitive data types: array and object data types in javascript are non-primitive and equality check never works for them unless the two operands are really pointing to the same location in memory.

Eg: {} == {} // false (both objects, however identical, point to 2 different memory locations so they are never 'equal')

Similarly, [1,2,3] == [1,2,3] // false (for the reason same as described for objects)

Coming to the sample code, I have a revised version for you to generate 'dataSplit' array identical to original 'data' array but never equal since they are two different variables, hence, different memory locations. The use of join and split, however, is correct. Revised sample:

function joinsplitPaste(){
  var data = [["mike",33,,"KS","male"],["jan",32," ","KS","female"],["dave",33,,"KS","male"],["mike",33, ,"KS","male"],["stan",31,,"KS","male"],["beth",19,"dataText","KS","female"]];
  var dataJoin = [];
  for (i = 0;i<data.length;i++){
    dataJoin.push(data[i].join(" ")) ;
  }
  var dataSplit = [];
  for (i = 0;i<data.length;i++){
    dataSplit.push(dataJoin[i].split(" ")) ;
  }
}