Question

我一直在编写一些代码，将一个项目添加到本地存储阵列，但遇到了一个没有更新阵列的问题。由于localStorage不允许数组，我一直在转换为字符串。

function addItem(add_item) {

    if (localStorage.getItem("list_items") === null) {
        localStorage.setItem("list_items", "");
    }
    else {
        "Something has gone horribly wrong!"
    }

    // Check if item is already added
    if(existingEntries == null) existingEntries = [];
    else {
        existingEntries = JSON.parse(localStorage.getItem("list_items"));
    }

    // Set entry to the currently selected item
    var entry = add_item;

    // Check if item is in string
    var exists = existingEntries.includes(entry);

    // Add item if it's not already in the array
    if (exists == false) {
        existingEntries.push(entry);
        localStorage.setItem("list_items", JSON.stringify(existingEntries));
    }
}

由于某种原因，本地存储未使用添加的新值进行更新。任何想法为什么？提前谢谢。

Answer 1

你已经过度复杂了。

简化为：

function addItem(add_item) {

  // parse existing storage key or string representation of empty array
  var existingEntries = JSON.parse(localStorage.getItem("list_items") || '[]');

  // Add item if it's not already in the array, then store array again
  if (!existingEntries.includes(add_item)) {
    existingEntries.push(add_item);
    localStorage.setItem("list_items", JSON.stringify(existingEntries));
  }else{
     // or tell user it's already there
     console.log(add_item + ' already exists')
  }
}

Answer 2

如果您的本地存储区中的数据包含密钥'list_items'，则localStorage.setItem("list_items", "my new data");将覆盖旧数据。

将数据添加到现有本地存储？的JavaScript

2 个答案: