1. for (i = 0; i < key; i++) {
    2.     mainArray[i] = Array(ptext.length);
    3.     for (s = 0; s < ptext.length; s++) {
    4.         mainArray[i][s] = "";

    key为3 ptext长度为5则数组为 3行5列！

    1. array = [ ['', '', '', '', '', ],
    2.           ['', '', '', '', '', ],
    3.           ['', '', '', '', '', ] ]