1.         // 比较版本号
    2.         // Return 1 if a > b
    3.         // Return -1 if a < b
    4.         // Return 0 if a == b
    5.         function compare(a, b) {
    6.           if (a === b) {
    7.             return 0;
    8.           }
    10.           var a_components = a.split(".");
    11.           var b_components = b.split(".");
    13.           // Math.min(x,y) 返回最低的值
    14.           var len = Math.min(a_components.length, b_components.length);
    16.           // 组件相等时循环
    17.           // loop while the components are equal
    18.           for (var i = 0; i < len; i++) {
    19.             // A bigger than B
    20.             if (parseInt(a_components[i]) > parseInt(b_components[i])) {
    21.               return 1;
    22.             }
    24.             // B bigger than A
    25.             if (parseInt(a_components[i]) < parseInt(b_components[i])) {
    26.               return -1;
    27.             }
    28.           }
    30.           // If one's a prefix of the other, the longer one is greater.
    31.           if (a_components.length > b_components.length) {
    32.             return 1;
    33.           }
    35.           if (a_components.length < b_components.length) {
    36.             return -1;
    37.           }
    39.           // Otherwise they are the same.
    40.           return 0;
    41.         }
    43.         console.log(compare("1", "2")); // -1
    44.         console.log(compare("2", "1")); // 1
    46.         console.log(compare("1.0", "1.0")); // 0
    47.         console.log(compare("2.0", "1.0")); // 1
    48.         console.log(compare("1.0", "2.0")); // -1
    49.         console.log(compare("1.0.1", "1.0")); // 1