“ JSON.parse（str）”返回“意外令牌c”，但str是字符串

Question

I am trying the following (below), but when I want to wrap the JSON.parse then I get an error Unexpected Token C. I checked online for similar problems and it says that the input is already an object, thus the reason for throwing this error. However, I tried typeof str and it returned me String. Also accessing it by piecesString[0].col did not work - thus my input is not an object but indeed a string. What went wrong?

function generatePieces(nbPieces) {
                    console.log("** nbPieces: " + nbPieces)
                    var piecesString = "";
                    var piecesArray = [];
                    var colIter = 0;
                    var rowIter = 0;

                    for (var i = 0; i <= (nbPieces*nbPieces-1); i++) {

                        piecesString = piecesString + "{col:" + colIter + ",row:" + rowIter + "},"

                        colIter = colIter + 1;
                        if (colIter == (nbPieces)) {
                            //console.log("colIter = nbPieces")
                            colIter = 0;
                            rowIter = rowIter +1;
                        }

                    }

                    piecesString = piecesString.substring(0, piecesString.length - 1);
                    piecesString = "[" + piecesString + "]"

                    piecesString = '' + piecesString

                    console.log(piecesString)
                    piecesArray = JSON.parse(piecesString);

                    //console.log(piecesString)


                }; // end generate pieces

Answer 1

str is a JS string, but isn't a string representation of a JSON text.

A property name in JSON must be a string, not an identifier.

{ col: 123 } is a valid JavaScript object literal, but invalid JSON.

{ "col": 123 } is OK in both.

---

Do not attempt to build JSON by mashing strings together. It is more trouble then it is worth. Build a data structure in whatever programming language you are using at the time (JavaScript in this case) and then pass it through a JSON serialiser.

var pieces = [];
for (var i = 0; i <= (nbPieces*nbPieces-1); i++) {
    var piece = { col: colIter, row: rowIter };
    pieces.push(piece);
}
var json_text = JSON.stringify(pieces);