能给个建议吗TypeError: undefined is not an object (evaluating 'this.pages[a]')

[ERROR] : TypeError: undefined is not an object (evaluating 'this.pages[a]')
file name:js/mui.min.js
line no:2138（格式化后的行数）
以下是mui.min.js 2138行
_getPage: function(a, b) {
return this.loop ? a > this.itemLength - (b ? 2 : 3) ? (a = 1, time = 0) : (b ? -1 : 0) > a ? (a = this.itemLength - 2, time = 0) : a += 1 : (b || (a > this.itemLength - 1 ? (a = 0, time = 0) : 0 > a && (a = this.itemLength - 1, time = 0)), a = Math.min(Math.max(0, a), this.itemLength - 1)), this.pages[a][0]
},