使用 JavaScript 中缀到后缀转换器

编译器更容易理解和评估后缀表达式。所以这是一个使用 JavaScript 将中缀表达式转换为后缀表达式的转换器。

先决条件：

• 堆栈操作
• 中缀到后缀的转换
• 基本 JavaScript

方法：

• 按钮转换调用函数InfixtoPostfix()并且该函数使用 JavaScript 转换给定的中缀表达式。
• 显示后缀表达式。

HTML代码：

HTML

  

  
    
    
    
    
    
    
  
    
    Infix to Postfix & Prefix Converter
  
    
    

  

    
        
            
                Infix to Postfix Converter in JavaScript
            
        
    
    
  
        
        
            Enter Valid Infix Expression
        
        
        
        
  
        
        
            Convert
    
    
    
  
        
        
            Postfix Expression:-
            
            
        
    

  

CSS 代码：以下代码是上述 HTML 代码中使用的“infix.css”文件的内容。

body {
    background-color: #fff0c3;
}
  
.container-fluid {
    background-color: #6f459e;
    justify-content: center;
}
  
.navbar-brand mb-0 h1 {
    color: black;
  
}
  
.navbar-light .navbar-brand {
    color: white;
}
  
.navbar navbar-light bg-light {
    width: 100%;
  
}
  
.navbar {
    padding: 0%;
}
  
.navbar-brand {
    font-size: 1.8rem;
}
  
.navbar-light .navbar-brand:hover {
    color: white;
}
  
.inputdata {
    text-align: center;
    margin-top: 21vh;
}
  
.span1 {
    font-size: 2vw;
    font-weight: 500;
    color: black;
}
  
.input1 {
    width: 58vw;
    text-align: center;
    height: 3vw;
    place-items: center;
    font-size: 20px;
    border: 2px solid white;
    border-radius: 18px;
    margin-top: 2vw;
}
  
.btn1 {
    border: wheat;
    background-color: #6f459e;
    text-align: center;
    color: white;
    font-weight: 500;
    border-radius: 8px;
    margin-top: 1.5vw;
    width: 7vw;
    height: 6vh;
}
  
button:hover {
    background-color: #c694ff;
}
  
input:focus {
    outline: none;
}
  
.output {
    text-align: center;
}

JavaScript 代码：以下代码是上述 HTML 代码中使用的文件“script.js”的内容。

Javascript

// Created an empty array
var stackarr = [];
  
// Variable topp initialized with -1
var topp = -1;
  
// Push function for pushing 
// elements inside stack
function push(e) {
    topp++;
    stackarr[topp] = e;
}
  
// Pop function for returning top element
function pop() {
    if (topp == -1)
        return 0;
    else {
        var popped_ele = stackarr[topp];
        topp--;
        return popped_ele;
    }
}
  
// Function to check whether the passed
// character is operator or not
function operator(op) {
    if (op == '+' || op == '-' || 
        op == '^' || op == '*' || 
        op == '/' || op == '(' || 
        op == ')') {
        return true;
    }
    else
        return false;
}
  
// Function to return the precedency of operator
function precedency(pre) {
    if (pre == '@' || pre == '(' || pre == ')') {
        return 1;
    }
    else if (pre == '+' || pre == '-') {
        return 2;
    }
    else if (pre == '/' || pre == '*') {
        return 3;
    }
    else if (pre == '^') {
        return 4;
    }
    else
        return 0;
}
  
// Function to convert Infix to Postfix
function InfixtoPostfix() {
  
    // Postfix array created
    var postfix = [];
    var temp = 0;
    push('@');
    infixval = document.getElementById("infixvalue").value;
  
    // Iterate on infix string
    for (var i = 0; i < infixval.length; i++) {
        var el = infixval[i];
  
        // Checking whether operator or not
        if (operator(el)) {
            if (el == ')') {
                while (stackarr[topp] != "(") {
                    postfix[temp++] = pop();
                }
                pop();
            }
  
            // Checking whether el is (  or not
            else if (el == '(') {
                push(el);
            }
  
            // Comparing precedency of el and
            // stackarr[topp]
            else if (precedency(el) > precedency(stackarr[topp])) {
                push(el);
            }
            else {
                while (precedency(el) <= 
                    precedency(stackarr[topp]) && topp > -1) {
                    postfix[temp++] = pop();
                }
                push(el);
            }
        }
        else {
            postfix[temp++] = el;
        }
    }
  
    // Adding character until stackarr[topp] is @
    while (stackarr[topp] != '@') {
        postfix[temp++] = pop();
    }
  
    // String to store postfix expression
    var st = "";
    for (var i = 0; i < postfix.length; i++)
        st += postfix[i];
  
    // To print postfix expession in HTML
    document.getElementById("text").innerHTML = st;
}

输出：