子字符串似乎不起作用

Question

getProductType = function (product) {
    var productType = '';
    if (product.standardVariable) {
        productType += 'Standard Variable, ';
    }
    if (product.basic) {
        productType += 'Basic, ';
    }
    if (product.intro) {
        productType += 'Intro, ';
    }
    if (product.fixed) {
        productType += 'Fixed, ';
    }
    if (product.equity) {
        productType += 'Equity';
    } else {
        alert(productType);
        productType.substring(0, productType.length - 2);
        alert(productType);
    }
    return productType;
};

My test case is that product.fixed = true, everything else is false.

Why is it that both my alerts print out 'Fixed, '? Why is substring not working?

Answer 1

try Assinging the value to variable because,substring returns a new string.

var newstr = productType.substring(0, productType.length - 2);
alert(newstr);

Answer 2

Strings are immutable in JavaScript. Also, .substring returns a new string. You'll need to assign the results of the substring to a variable. You can reuse productType for this, so this should do the job:

productType = productType.substring(0, productType.length - 2);