Question

I m trying to create a simple calculator in Javascript. I have an array named expression chunk[0] = 12 chunk[1] = + (the "+" sign) chunk[1] = 5

我曾用 lo子(草) lo,然后加入如下单一表述:

equation = ""; // To make var equation a string

for(i = 0; i <= length; i++)
{
    equation = equation + expression[i];
    alert(expression[i]);
}

alert(equation);

alert(expression[i]) showed values 12, + and 5. But alert(equation) showed 125 (instead of "12+5"). I need the variable equation to be "12+5" so that I can later call eval(equation) and get the value of 12+5.

我在这里做了什么错误?

Answer 1

如果您有chunk = [12, + , 5];, 那么你可以做var eq = chunk.join(");,然后通过

Answer 2

你做了哪些错误? 你们有一个小体。

修订关于这个问题的法典

chunk[0] = 12
chunk[1] =  + 
chunk[1] = 5

纽约总部

chunk[0] = 12
chunk[1] =  + 
chunk[2] = 5

And everything should work.

Why this works: Both the + and the 5 are being assigned 纽约总部chunk[1], with the 5 over-writing the previous assignment ( 纽约总部chunk[1]) of +. This also explains why the concatenated value displayed is 125

In order, the first assignment results in a collection with
a member chunk[0] and a content of 12

The second assignment adds a new member, and results in a collection with
a member chunk[0] whose content is 12
a member chunk[1] whose content is +

The third assignment overwrites the 2nd member, and results in a collection with
a member chunk[0] whose content is 12
a member chunk[1] whose content is 5

all=125

希望化=<代码>12+5

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