设计一个程序,统计字符串中出现最多的单词

function word(str){
    var newStr = str.toLocaleLowerCase();
    var obj = {};
    var arr = newStr.split(" ");
    var maxWord = null;
    arr.map(function (t) {
        if(obj[t]){
            obj[t].num ++;
            if(maxWord.num < obj[t].num){
                maxWord = obj[t];
            }
        }else {
            var w = {
                num: 1,
                value: t
            };
            if(!maxWord){
                maxWord = w;
            }
            obj[t] = w;
        }
    })
    return maxWord
}
// 测试数据
var str="The indictment said said said said the be defendants had collected geographical data "+
    "indicating thousands of people would be killed in the chemical blast";
console.log(word(str));