javascript代码在while循环后将无法运行

Question

I am trying to write a loop that inspects a string to see if a stored variable is contained within the string, and then replaces that variable with the stored value. I have that part working fine, however after my while loop the code stops and will not run. Here is the code:

 var output = document.getElementById('output'); String.prototype.replaceAll = function(search, replacement) { var target = this; return target.split(search).join(replacement); }; var sortedVarArray = [ //[varName, value, units, complex?] ["d", 2, null, 0], ["h", 3, null, 0], ["u", "d + h", null, 1] ]; var value = 'u + 1'; var complex = true; while (complex) { complex = false; for (var i = 0; i -1 < sortedVarArray.length; i++) { if (value.indexOf(sortedVarArray[i][0]) > -1 && sortedVarArray[i][3] == 1) complex = true; value = value.replaceAll(sortedVarArray[i][0], sortedVarArray[i][1]); if (complex) break; } output.innerHTML += "<br> hello"; } output.innerHTML += "<br> hello2"; var result = eval(value); output.innerHTML += "<br> result = " + result; 

 <div id="output"></div> 

so if, for example, I have an array sortedVarArray that looks like:

sortedVarArray = [
    ["varName", "value", "units", "complex?"]
    ["d", 2, null, 0]
    ["h", 3, null, 0]
    ["u", "d + h", null, 1]
]

and an equation value equal to u + 1

which, as the loop progresses, should change to look like this:

u + 1
d + h + 1
2 + h + 1
2 + 3 + 1

which will then evaluate to 6 at the end

My problem is that the code does not make it out of the for loop unless it breaks , and then it does not make it out of the while loop. and my code never evaluates.

I have a bunch of output messages in my code (cleaned up for here) and I can see that the string value is being modified as desired as the code loops. I am just not sure why it is not continuing after the loop ends.

Oh and if I change the code so that complex is declared as false, the loop is skipped and "hello2" is printed to output .

Thanks in advance,

Dan

EDIT: the ReplaceAll function is contained in the start of the script (outside of any function) and is as follows:

String.prototype.replaceAll = function(search, replacement) {
    var target = this;
    return target.split(search).join(replacement);
};

Answer 1

in your for loop:

i - 1 < sortedVarArray.length

will iterate your array for index 0 to length, where array[length] = undefined. try:

i < sortedVarArray.length