菲薄数列

/** * Created by wangchaomac on 2017/3/13. *//*1.斐波那契数列**/function fbnq(sqIndex){    var firstNo = 1;    var secondNo = 1;    if( sqIndex < 2 ) {        if( sqIndex < 0) {

            return ‘error input param‘;        }        return 1;    }

    var fbnqNo = -1;

    for(var fbnqIndex = 2; fbnqIndex < sqIndex ; fbnqIndex ++) {

        fbnqNo = firstNo + secondNo ;        firstNo = secondNo ;        secondNo =  fbnqNo ;    }

    return fbnqNo;

}alert(fbnq(4));