Question

我正在尝试为chrome创建一个简单的计算器。我需要使用eval（）来计算表达式，但它被chrome禁止。任何解决方法？这是js。任何人都可以解决这个问题吗？我到处寻找。

var text = document.getElementById("tBox");
var x = 0;
var y = 0;
var op = "";
var resetFlag = 0;

document.getElementById("buttonbackspace").addEventListener("click",function(){backspace()});

document.getElementById("buttonone").addEventListener("click",function(){addDigit(1)});

document.getElementById("buttontwo").addEventListener("click",function(){addDigit(2)});

document.getElementById("buttonthree").addEventListener("click",function(){addDigit(3)});

document.getElementById("buttonfour").addEventListener("click",function(){addDigit(4)});

document.getElementById("buttonfive").addEventListener("click",function(){addDigit(5)});

document.getElementById("buttonsix").addEventListener("click",function(){addDigit(6)});

document.getElementById("buttonseven").addEventListener("click",function(){addDigit(7)});

document.getElementById("buttoneight").addEventListener("click",function(){addDigit(8)});

document.getElementById("buttonnine").addEventListener("click",function(){addDigit(9)});

document.getElementById("buttonzero").addEventListener("click",function(){addDigit(0)});

document.getElementById("buttondecimal").addEventListener("click",function(){addDigit(".")});

document.getElementById("buttonaddition").addEventListener("click",function(){add()});

document.getElementById("buttonsubtraction").addEventListener("click",function(){subtract()});

document.getElementById("buttonmultiplication").addEventListener("click",function(){multiply()});

document.getElementById("buttondivision").addEventListener("click",function(){divide()});

var backspace = function() {
    tBox.value = tBox.value.slice(0, -1);
};
var addDigit = function(x) {
    tBox.value = tBox.value + x;
}
var add = function() {
    if (x === 0) {
        x = tBox.value;
        tBox.value = "";
        op = "+";
    } else if (y === 0) {
        y = tBox.value;
        equals();
    }
};
var subtract = function() {
    if (x === 0) {
        x = tBox.value;
        tBox.value = "";
        op = "-";
    } else if (y === 0) {
        y = tBox.value;
        equals();
    }
};
var multiply = function() {
    if (x === 0) {
        x = tBox.value;
        tBox.value = "";
        op = "*";
    } else if (y === 0) {
        y = tBox.value;
        equals();
    }
};
var divide = function() {
    if (x === 0) {
        x = tBox.value;
        tBox.value = "";
        op = "/";
    } else if (y === 0) {
        y = tBox.value;
        equals();
    }
};
var equals = function() {
    y = tBox.value;
    tBox.value = eval(x + op + y); //Eval over here
    x = 0;
    y = 0;
    resetFlag = 1;
};

Answer 1

我无所事事......好吧，我让你成为评估数学的函数：

var eval = function( maths ){
    // Lets start

    var math_object = [];
    var number = 0;
    var pattern;

    while( maths.length>0 ){
        // get front number
        number = parseFloat( maths );
        // create regexp pattern
        pattern = new RegExp('^'+((number>=0)?'\\+*':'')+number.toString(), 'i');
        // check for error
        if( isNaN(number) || !maths.match(pattern) ) return "Expression Error";
        // cut number from string
        maths = maths.replace(pattern,'');
        // push number into array
        math_object.push(number);
        // Check if next has action
        if( maths.length==0 ) break;
        // get math action
        if( !maths[0].match(/[\/\*+-]/i) ) return "Expression Error";
        // save acton
        if( maths[0].match(/[+-]/i) ){
            math_object.push('+');
        }else{
            math_object.push(maths[0]);
            maths = maths.substr(1);
        }
    }

    if( math_object.length%2==0 ) return "Expression Error";
    if( math_object.length==1 ) return math_object[0];

    //console.log(math_object);

    var math_object_structed = [];

    var i = 0;
    while( i<math_object.length ){
        if( i+1==math_object.length ){
            math_object_structed.push(math_object[i]);
            break;
        }
        if( math_object[i+1]=='+' ){
            math_object_structed.push(math_object[i]);
            math_object_structed.push('+');
            i+=2;
        }else{
            var array = [
                math_object[i],
                math_object[i+1],
                math_object[i+2]
            ];
            math_object.splice(i, 2);
            math_object[i] = array;
        }
    }

    //console.log(math_object_structed);

    var doMath = function( math_array ){
        while( math_array.length>1 ){
            var first = math_array.shift();
            if( typeof first != "number" )
                first = doMath( first );

            var action = math_array.shift();

            var second = math_array.shift();
            if( typeof second != "number" )
                second = doMath( second );

            var result;
            if( action=='+' )
                result = first + second;
            else if( action=='*' )
                result = first * second;
            else if( action=='/' )
                result = first / second;
            else
                return "Expression Error";

            math_array.unshift( result );
        }

        if( typeof math_array[0] != "number" )
            return doMath( math_array[0] );
        else
            return math_array[0];
    }

    return doMath( math_object_structed );
}

现在1+2+3/5+14*3*4*5+16的结果是859.6 我的函数eval("1+2+3/5+14*3*4*5+16")的结果是859.6

快乐的编码。

Answer 2

您可以使用HTML5 Filesystem API首先将您想要eval的代码写入本地文件系统，然后eval执行该脚本。

第一步是请求文件系统：

navigator.webkitPersistentStorage.requestQuota(FILESYSTEM_RESOURCES_QUOTA_MB * 1024 * 1024, function (grantedBytes) {
    console.log('Granted ' + grantedBytes + ' bytes for filesystem.');
    window.webkitRequestFileSystem(window.PERSISTENT, grantedBytes, onInitFs, errorHandler);
}, errorHandler);

function onInitFs(fs) {  
    // File system initialized
}

初始化文件系统后，在文件系统上创建一个临时文件并加载脚本：

fs.root.getFile('my-script.js', {create: true}, function(fileEntry) {  
    // Create a FileWriter object for our FileEntry (log.txt).
    fileEntry.createWriter(function(fileWriter) {

        fileWriter.onwriteend = function(e) {
            console.log('Write completed.');

            // Execute the script 
            $.getScript(fileEntry.toURL());
        };

        fileWriter.onerror = function(e) {
            console.log('Write failed: ' + e.toString());
        };

        // Create a new Blob and write it to my-script.js.
        var blob = new Blob([scriptText], {type: 'text/plain'});
        fileWriter.write(blob);
    }, errorHandler);
}, errorHandler);

Answer 3

阅读Chrome文档"Using eval in Chrome Extensions. Safely."。它回答了这个常见问题。

Chrome app eval（）

3 个答案: