javascript - 函数输出替换了我的主要 JSON 字符串的前两行
问题描述
我有一个 JSON 查询，我正在使用console.log它来展示它：
var json_data = {"headers":["Month","Value","Number"],"rows":[["2018-10-01 00:00:00.0","one",209],["2018-09-01 00:00:00.0","one",274],["2018-09-01 00:00:00.0","five",183],["2018-10-01 00:00:00.0","five",164],["2018-09-01 00:00:00.0","four",214],["2018-10-01 00:00:00.0","four",192],["2018-09-01 00:00:00.0","three",128],["2018-10-01 00:00:00.0","three",125],["2018-09-01 00:00:00.0","two",199],["2018-10-01 00:00:00.0","two",169],["2018-09-01 00:00:00.0","seven",10541],["2018-10-01 00:00:00.0","seven",6139],["2018-10-01 00:00:00.0","six",169],["2018-09-01 00:00:00.0","six",233]]};
document.getElementById("original").innerHTML = json_data.rows;
<div style="background:yellow; "id="original"></div>
<div style="background:red;" id="output"></div>对于值“一”，我有两个数字（209和274）。
然后我使用一个函数来分组，它工作正常（输出）。我的问题是，当我使用console.log初始 json_data 查询时，前两行是不同的。看来我的函数用输出的行（红色）替换了前两行。函数在这里给出：
function initialGroupBy(rows) {
const
rowMap = new Map(),
result = [],
dataTemp = [];
// Iterate over the rows.
rows.forEach(row => {
const
// Create a key, it is the first elements joined together.
key = row.slice(0,1).join();
// Check if the Map has the generated key...
if (rowMap.has(key)) {
// The map has the key, we need to add up the values
const
// Get the value for the current key.
storedRow = rowMap.get(key);
// Add the value of the current row to the row in the map.
storedRow[2] += row[2];
} else {
// The key doens't exist yet, add the row to the map.
rowMap.set(key, row);
}
});
// Iterate over all the entries in the map and push each value with the
// summed up value into the array.
rowMap.forEach(value => {
result.push(value);
});
for (i = 0; i < result.length; i++)
{
var object2 = {"date": result[i][0].slice(0,7), "num": result[i][2]};
dataTemp.push(object2);
}
return dataTemp;
}
可以在此处找到完整的片段（比较两个片段中黄色框的前两行）：
var json_data = {"headers":["Month","Value","Number"],"rows":[["2018-10-01 00:00:00.0","one",209],["2018-09-01 00:00:00.0","one",274],["2018-09-01 00:00:00.0","five",183],["2018-10-01 00:00:00.0","five",164],["2018-09-01 00:00:00.0","four",214],["2018-10-01 00:00:00.0","four",192],["2018-09-01 00:00:00.0","three",128],["2018-10-01 00:00:00.0","three",125],["2018-09-01 00:00:00.0","two",199],["2018-10-01 00:00:00.0","two",169],["2018-09-01 00:00:00.0","seven",10541],["2018-10-01 00:00:00.0","seven",6139],["2018-10-01 00:00:00.0","six",169],["2018-09-01 00:00:00.0","six",233]]};
function initialGroupBy(rows) {
const
rowMap = new Map(),
result = [],
dataTemp = [];
// Iterate over the rows.
rows.forEach(row => {
const
// Create a key, it is the first elements joined together.
key = row.slice(0,1).join();
// Check if the Map has the generated key...
if (rowMap.has(key)) {
// The map has the key, we need to add up the values
const
// Get the value for the current key.
storedRow = rowMap.get(key);
// Add the value of the current row to the row in the map.
storedRow[2] += row[2];
} else {
// The key doens't exist yet, add the row to the map.
rowMap.set(key, row);
}
});
// Iterate over all the entries in the map and push each value with the
// summed up value into the array.
rowMap.forEach(value => {
result.push(value);
});
for (i = 0; i < result.length; i++)
{
var object2 = {"date": result[i][0].slice(0,7), "num": result[i][2]};
dataTemp.push(object2);
}
return dataTemp;
}
const damn = initialGroupBy(json_data.rows);
document.getElementById("original").innerHTML = json_data.rows;
document.getElementById("output").innerHTML =JSON.stringify(damn);<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div style="background:yellow; "id="original"></div>
<br><br>
<div style="background:red;" id="output"></div>在很多情况下，我都尝试过将其更改为var。const我在这里错过了一个基本JavaScript案例吗？