Question

我在运行代码时遇到此控制台错误：

未捕获的TypeError：无法读取未定义的属性'length'

完整日志

at renderUserBlocks (eval at globalEval (jquery.min.js:2), <anonymous>:692:47)
    at Object.success (eval at globalEval (jquery.min.js:2), <anonymous>:242:17)
    at i (jquery.min.js:2)
    at Object.fireWith [as resolveWith] (jquery.min.js:2)
    at z (jquery.min.js:4)
    at XMLHttpRequest.<anonymous> (jquery.min.js:4)

我的代码

function renderUserBlocks(blocksResults){
        var $blocksRows = $('#blocks_rows');
        for (var i = 0; i < blocksResults.length; i += 2){
            var block = parseUserBlock(blocksResults[i + 1], blocksResults[i]);
            var blockJson = JSON.stringify(block);
            var existingRow = document.getElementById('blockRow' + block.time);
            if (existingRow && existingRow.getAttribute('data-json') !== blockJson){
                $(existingRow).replaceWith(getUserBlockRowElement(block, blockJson));
                $('[data-toggle="tooltip"]').tooltip();
            }
            else if (!existingRow){
                var blockElement = getUserBlockRowElement(block, blockJson);
                var inserted = false;
                var rows = $blocksRows.children().get();
                for (var f = 0; f < rows.length; f++) {
                    var pTime = parseInt(rows[f].getAttribute('data-time'));
                    if (pTime < block.time){
                        inserted = true;
                        $(rows[f]).before(blockElement);
                        break;
                    }
                }
                if (!inserted)
                    $blocksRows.append(blockElement);
                    $('[data-toggle="tooltip"]').tooltip();
            }
        }
    }

此行显示错误

for (var i = 0; i < blocksResults.length; i += 2)

Answer 1

这是因为blocksResults是null，并且它没有length属性。
您可以在for循环之前检查它

if (blocksResults) {loop here}

无法读取JavaScript上未定义的属性“长度”

1 个答案: