为什么这个JavaScript在浏览器中不起作用
Why doesn't this javascript work in browser?
我在.js文件中有以下代码：
$.extend(KhanUtil, {
// takes a number and returns the sign of that number
steveSign: function(num){
num = parseFloat(num)
if (num>=0){return 1}
else{return -1}
},
// takes a function, a lower bound for a zero,an upper bound for a zero, and locates
// that zero by iteratively halving the interval.
steveRoot: function(f,xmin,xmax){
var l = xmin
var r = xmax
var z = 0
for (i=0;i<6;i++){
z = (l + r)/2
if (KhanUtil.steveSign(f(l)) === KhanUtil.steveSign(f(z))){ l = z}
else{r = z}
}
return z
},
});
在我的 html 文件中，我定义了var f = function(x){return x**2 - 2}并运行steveRoot(f,1,2)，但我的浏览器崩溃了。 为什么会这样？
编辑：
我正在发布我的全部代码，因为它是在评论中要求的。 感谢一群人试图帮助我。 奇怪的是代码在十次中有 9 次运行良好。 只是偶尔会"掰子"。 这里有很多随机变量，但我无法想象为什么 steveRoot 会关心获得一个稍微不同的函数。 代码工作得很好，当我不包含调用 steveRoot 的变量时，它永远不会废话。
该 HTML 文件：
<!DOCTYPE html>
<html data-require="math graphie graphie-helpers play polynomials steveMath">
<head>
<title>Piecewise-defined function</title>
<script src="../khan-exercise.js"></script>
</head>
<body>
<div class="exercise">
<div class="vars">
<var id = "n">randRange(2,4)</var>
<var id = "abscissas">makeXList()</var>
<var id = "ordinates">makeYList(-9,9,abscissas.length)</var>
<var id = "points">makeCoordinates(abscissas,ordinates)</var>
<var id = "f">(function(x){return niceFunction(x,points)})</var>
<var id = zeros>steveRoot(f,-10,10)</var>
</div>
<div class="problems">
<div id="problem-type-or-description">
<p class="problem">You are going to have to answer 5</p>
<p class="question">Answer 5</p>
<div class="graphie" id="grid">
graphInit({
range: 10,
scale: 20,
tickStep: 1,
axisArrows: "<->"
});
a =style({
stroke: "red",
strokeWidth: 2
}, function() {
plot( function( x ) { return niceFunction(x,points);
}, [ -10, 10 ] );
});;
a.plot();
</div>
<p class="solution">5</p>
</div>
</div>
<div class="hints">
<!-- Any hints to show to the student. -->
</div>
</div>
</body>
.js文件：
$.extend(KhanUtil, {
//randomLines is a piecewise linear function in x, where the partition points are given by list_of_points.
//list_of_points is an array of arrays, for example [[1,5],[2,-1],[3,4]] would indicate the points (1,5), (2,-1), and (3,4)
//are on the curve. The points must be arranged in order of increasing abscissa.
randomLines: function(x,list_of_points)
{
for (i=0;i<list_of_points.length-1;i++)
{
var x_1 = list_of_points[i][0]
var y_1 = list_of_points[i][1]
var x_2 = list_of_points[i+1][0]
var y_2 = list_of_points[i+1][1]
var m = (y_2-y_1)/(x_2-x_1)
var y = m*(x - x_1) + y_1
if (x > x_1 && x <= x_2){return y}
}
if (x<=list_of_points[0][0]){return 0}
if (x>list_of_points[list_of_points.length-1][0]){return 0}
},
//randomLinesFunc: function(list_of_points){
// var f = function(x){
// return randomLines(x,list_of_points)
// }
//
// return f
//},
numInt: function(f,x){
var delta = .01
var sum = 0
var i = 0
while ((delta*i-10)<=x)
{sum = sum+delta*f(-10+i*delta)
i++
}
return sum
},
peace: function(x){return 2},
////////////////////////////////////////////////
//randRangeNZCU takes (min,max,n) and returns an array of nonzero numbers between max and min
//with successive numbers being distinct. For example [-1,2,-1] could show up, but [2,2,5] will not.
// NZCU stands for NonZeroConsecutiveUnique.
randRangeNZCU: function(min,max,n){
excluded = [0]
array = [KhanUtil.randRangeExclude(min,max,excluded)]
for (i=1;i<n;i++){
excluded = [0,array[i-1]]
array.push(KhanUtil.randRangeExclude(min,max,excluded))
}
return array
},
// makeCoordinates takes two arrays of the same length and returns the array of ordered pairs.
// Example: makeCoordinates([1,2,3],[4,5,6]) = [[1,4],[2,5],[3,6]]
makeCoordinates: function(array1,array2){
array = []
for (i=0;i<array1.length;i++){
array.push([array1[i],array2[i]])
}
return array
},
steveCubic: function(x){return -Math.pow(x,3)/2+3*x/2},
//niceFunction is a C^1 function which connects the points in "points". It is designed to be used
//in my "curveSketchingIntuition" exercise. Every point in the list will have 0 slope, except the first and last point.
niceFunction: function(x,points){
len = points.length
var x1 = points[0][0]
var x2 = points[1][0]
var y1 = points[0][1]
var y2 = points[1][1]
var k = (y1 - y2)/Math.pow(x1-x2,2)
if (x<x2){return k*Math.pow(x-x2,2)+y2}
for (i=1;i<len-2;i++){
var x1 = points[i][0]
var x2 = points[i+1][0]
var y1 = points[i][1]
var y2 = points[i+1][1]
xNew = (x-x1)*2/(x2-x1)-1
yNew = (KhanUtil.steveCubic(xNew)+1)*(y2-y1)/2+y1
if (x>=x1 && x<x2){return yNew}
}
var x1 = points[len-2][0]
var x2 = points[len-1][0]
var y1 = points[len-2][1]
var y2 = points[len-1][1]
var k = (y2 - y1)/Math.pow(x1-x2,2)
if (x>=x1){return k*Math.pow(x-x1,2)+y1}
},
makeXList: function(){
array = [-10]
i=0
while(array[i]<10){
x = array[i]+3*KhanUtil.randRange(1,3)
if (x<10){array.push(x)}
i=i+1
}
array.push(10)
return array
},
makeYList:function(min,max,n){
excluded = [0]
array = [KhanUtil.randRangeExclude(min,max,excluded)]
excluded.push(array[0])
array.push[KhanUtil.randRangeExclude(min,max,excluded)]
excluded = [0]
for (i=1;i<n;i++){
if (array[i-2]<array[i-1]){
array.push(KhanUtil.randRangeExclude(min,array[i-1]-1,excluded))
}
else{array.push(KhanUtil.randRangeExclude(array[i-1]+1,max,excluded))}
}
return array
},
newtonRoot: function(f,a){
var z = a
var m = (f(z+.01)-f(z-.01))/.02
for(i=0;i<2;i++){
z = z-f(z)/m
m = (f(z+.01)-f(z-.01))/.02
}
return z
},
steveSign: function(num){
num = parseFloat(num)
if (num>=0){return 1}
else{return -1}
},
steveRoot: function(f,xmin,xmax){
var l = xmin
var r = xmax
var z = 0
for (i=0;i<6;i++){
z = (l + r)/2
if (KhanUtil.steveSign(f(l)) === KhanUtil.steveSign(f(z))){ l = z}
else{r = z}
}
return z
},
locateZeros: function(f,points){
var len = points.length
var list = []
for(i=0;i<len-1;i++){
var x0 = points[i][0]
var x1 = points[i+1][0]
var y0 = points[i][1]
var y1 = points[i+1][1]
// var m = (y1-y0)/(x1-x0)
// var a = -y0/m+x0
// var z = KhanUtil.steveRoot(f,1,2)
list.push(KhanUtil.steveSign(f(x0)))
}
return list
},
}）;
-
在javascript中，
x**2是无效的。（SyntaxError: Unexpected token *） -
您需要运行
KhanUtil.steveRoot(f,1,2);而不仅仅是steveRoot(f,1,2);.
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