中缀表达式转后缀表达式（用于求字符串表达式值）（js栈和队列的实现是通过数组的push和unshift方法插值，pop方法取值）

//        var expression = ‘(1+2)*((8-2)/(7-4))‘;
        var expression =‘3+(2-5)*6/3‘
        var obj = {‘+‘: 0, ‘-‘: 0, ‘*‘: 1, ‘/‘: 1, ‘(‘: -1};
        var arr = [];
        var str = ‘‘;
        for (var i = 0; i < expression.length; i++) {
            var curChar = expression[i];
            if (curChar == ‘ ‘) {
                continue;
            }
            var num = /^\d$/.test(curChar);
            if (num) {
                str = str + curChar + ‘ ‘;
                continue;
            } else if (curChar == ‘(‘) {
                arr.push(curChar);
            } else if (curChar == ‘)‘) {
                var len = arr.length;
                for (var j = 0; j < len; j++) {
                    var pop = arr.pop();
                    if (pop != ‘(‘) {
                        str = str + pop + ‘ ‘;
                    } else {
                        break;
                    }
                }
            } else {
                if (arr.length > 0) {
                    var top = arr[arr.length - 1];
                    if (obj[curChar] > obj[top]) {
                        arr.push(curChar);
                    } else {
                        var pop = arr.pop();
                        arr.push(curChar);
                        str = str + pop + ‘ ‘;
                    }
                } else {
                    arr.push(curChar);
                }
            }
        }
        for(var i=arr.length-1;i>=0;i--){
            str = str + arr[i] + ‘ ‘;
        }
        console.log(str);