Uncaught TypeError：無法讀取undefined（array）的屬性「長度」

下面是我爲Phonegap項目開發的一段代碼。Uncaught TypeError：無法讀取undefined（array）的屬性「長度」

我試圖繪製與供給的角度（sensorAngles陣列）的曲線。這個數組將通過藍牙更新（首先作爲字符串發送），因此如果接收到的數據沒有損壞（也就是每個陣列中沒有空或錯誤的元素，全長），我只需要更新曲線。

我現在正通過setTimeout通過更新角度陣列'模擬'藍牙串行更新。

當前，腳本按預期工作（曲線在損壞的數組/字符串時不會繪圖/更新，並在接收到非損壞數組後繼續更新），但是我收到上述錯誤（未捕獲的類型錯誤）。

它似乎與第26行有關，其中corrupt array使sensorAngles未定義（所以.length不起作用）。

for (var i = 0; i < (sensorAngles.length); i++){ 
    sensorPos.push({ 
     x: sensorPos[i].x - diffPos(sensorAngles[i]).dx, 
     y: sensorPos[i].y - diffPos(sensorAngles[i]).dy 
    }); 

}

我曾嘗試添加if語句，但曲線將不再更新。

我剛開始使用Javascript和Phonegap 2天前，所以任何幫助將是偉大的！

乾杯， JD

整個代碼：

var stage = new Kinetic.Stage({ 
    container: 'myCanvas', 
    width: window.innerWidth, 
    height: window.innerHeight 
}); 

var sensorLayer = new Kinetic.Layer(); 

/* initialise an empty array of all the angles */ 
var sensorAngles = [0, 0, 0, 0, 0, 0, 0, 0]; 
//var sensorPos = []; 

/* divide each sensor distance segment by height of screen/window for 
maximum amount of canvas being used */ 
var sensorDistance = (stage.getHeight()/((sensorAngles.length) + 2)); 

function diffPos(angle){ // angles in radians 
    return { 
     dx: sensorDistance * Math.sin(angle), 
     dy: sensorDistance * Math.cos(angle) 
    } 
}; 

function calcSpline(sensorAngles){ 
    sensorPos = [{x: (stage.getWidth()/2), y: (stage.getHeight() - sensorDistance)}]; 
    for (var i = 0; i < (sensorAngles.length); i++){ 
     sensorPos.push({ 
      x: sensorPos[i].x - diffPos(sensorAngles[i]).dx, 
      y: sensorPos[i].y - diffPos(sensorAngles[i]).dy 
     }); 

    } 
    return sensorPos; 
}; 

calcSpline(sensorAngles); 

var sensorPos = calcSpline(sensorAngles); 
var spine = new Kinetic.Spline({ 
    points: sensorPos, 
    stroke: 'red', 
    strokeWidth: 2, 
    lineCap: 'round', 
    tension: 0.3 
}); 

sensorLayer.add(spine); 
stage.add(sensorLayer); 



function updateSpline(angles){ 
    calcSpline(sanityCheck(angles)); 
    spine.setPoints(sensorPos); 
    sensorLayer.draw(); 
}; 

function sanityCheck(data) { 
    data = data.split(","); 
    if (data.filter(function(n){return n}).length === sensorAngles.length) { 
     sensorAngles = data; 
     return sensorAngles; 
    } 
} 

setTimeout(
    function() { 
     updateSpline("0.1,0.12,0.08,-0.2,0.1,0.85,0.1,-0.2") 
    },1000 
); 
setTimeout(
    function() { 
     updateSpline("0.1,0.2,0.1,-0.1,0.1,0.1,0.1,-0.2") 
    },2000 
); 
setTimeout(
    function() { 
     updateSpline("0.1,0.12,0.08,-0.2,0.1,0.85,0.1,-0.2") 
    },3000 
); 
setTimeout(
    function() { 
     updateSpline("0.4,0.5,,-0.6,0.2,0.96,0.02,-0.01") //corrupt 
    },4000 
); 
setTimeout(
    function() { 
     updateSpline("0.1,,0.08,-0.2,0.1,0.85,0.1,-0.2") // corrupt 
    },5000 
); 

setTimeout(
    function() { 
     updateSpline("0.6,0.12,0.22,-0.2,0.1,0.85,0.1,-0.2") 
    },6000 
);

來源

2013-07-24 Jian

你可以使用try ... catch塊忽略損壞的陣列。

http://jsfiddle.net/wC79k/1/

try { 
for (var i = 0; i < (sensorAngles.length); i++){ 
    sensorPos.push({ 
     x: sensorPos[i].x - diffPos(sensorAngles[i]).dx, 
     y: sensorPos[i].y - diffPos(sensorAngles[i]).dy 
    }); 

} 
}catch(err){ 
    // console.log("oops"); 
}

來源

2013-07-24 17:57:31

Uncaught TypeError：無法讀取undefined（array）的屬性「長度」

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