@mapgis/webclient-common
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An important part of the MapGIS Client for JavaScript product, which provides interfaces and functions unrelated to the map engine.
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<h1> MapGIS Client for JavaScript API</h1>
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Common
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Cesium-Plugin
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MapboxGL-Plugin
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<header id="page-title" class="page-title">
<span class="page-title-main">类名</span>
<span class="page-title-sub">表达式</span>
</header>
<section>
<header>
</header>
<article>
<h2>表达式说明</h2>
<p>目前表达式支持的功能</p>
<ul>
<li>
<p>链接符</p>
</li>
<li>
<p>数学运算符</p>
</li>
<li>
<p>条件运算符</p>
</li>
</ul>
<h4>链接符</h4>
<p>目前仅支持$feature链接符，支持访问要素的属性信息。
<strong>example</strong></p>
<pre class="prettyprint source"><code>$feature.FID //表示访问要素的FID字段
</code></pre>
<h4><strong>数学运算</strong></h4>
<p>支持一般通用数学运算符，如+-*/等计算符</p>
<p><strong>example</strong></p>
<p>计算面积占比</p>
<pre class="prettyprint source"><code>$feature.AREA/$feature.TOTALAREA
</code></pre>
<h4><strong>条件运算</strong></h4>
<p><strong>example</strong></p>
<p>支持 || and or >= <=等</p>
<pre class="prettyprint source"><code>$feature.ISAREA || $feature.ISRIVER
</code></pre>
<h3>后续拟支持的表达式运算符和内置函数</h3>
<h4>Operator Precedence</h4>
<table>
<thead>
<tr>
<th style="text-align:left">Operator</th>
<th style="text-align:left">Associativity</th>
<th style="text-align:left">Description</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align:left">(...)</td>
<td style="text-align:left">None</td>
<td style="text-align:left">Grouping</td>
</tr>
<tr>
<td style="text-align:left">f(), x.y, a[i]</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Function call, property access, array indexing</td>
</tr>
<tr>
<td style="text-align:left">!</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Factorial</td>
</tr>
<tr>
<td style="text-align:left">^</td>
<td style="text-align:left">Right</td>
<td style="text-align:left">Exponentiation</td>
</tr>
<tr>
<td style="text-align:left">+, -, not, sqrt, etc.</td>
<td style="text-align:left">Right</td>
<td style="text-align:left">Unary prefix operators (see below for the full list)</td>
</tr>
<tr>
<td style="text-align:left">*, /, %</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Multiplication, division, remainder</td>
</tr>
<tr>
<td style="text-align:left">+, -, ||</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Addition, subtraction, array/list concatenation</td>
</tr>
<tr>
<td style="text-align:left">==, !=, >=, <=, >, <, in</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Equals, not equals, etc. "in" means "is the left operand included in the right array operand?"</td>
</tr>
<tr>
<td style="text-align:left">and</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Logical AND</td>
</tr>
<tr>
<td style="text-align:left">or</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Logical OR</td>
</tr>
<tr>
<td style="text-align:left">x ? y : z</td>
<td style="text-align:left">Right</td>
<td style="text-align:left">Ternary conditional (if x then y else z)</td>
</tr>
<tr>
<td style="text-align:left">=</td>
<td style="text-align:left">Right</td>
<td style="text-align:left">Variable assignment</td>
</tr>
<tr>
<td style="text-align:left">;</td>
<td style="text-align:left">Left</td>
<td style="text-align:left">Expression separator</td>
</tr>
</tbody>
</table>
<h4>Unary operators</h4>
<table>
<thead>
<tr>
<th style="text-align:left">Operator</th>
<th style="text-align:left">Description</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align:left">-x</td>
<td style="text-align:left">Negation</td>
</tr>
<tr>
<td style="text-align:left">+x</td>
<td style="text-align:left">Unary plus. This converts it's operand to a number, but has no other effect.</td>
</tr>
<tr>
<td style="text-align:left">x!</td>
<td style="text-align:left">Factorial (x * (x-1) * (x-2) * … * 2 * 1). gamma(x + 1) for non-integers.</td>
</tr>
<tr>
<td style="text-align:left">abs x</td>
<td style="text-align:left">Absolute value (magnitude) of x</td>
</tr>
<tr>
<td style="text-align:left">acos x</td>
<td style="text-align:left">Arc cosine of x (in radians)</td>
</tr>
<tr>
<td style="text-align:left">acosh x</td>
<td style="text-align:left">Hyperbolic arc cosine of x (in radians)</td>
</tr>
<tr>
<td style="text-align:left">asin x</td>
<td style="text-align:left">Arc sine of x (in radians)</td>
</tr>
<tr>
<td style="text-align:left">asinh x</td>
<td style="text-align:left">Hyperbolic arc sine of x (in radians)</td>
</tr>
<tr>
<td style="text-align:left">atan x</td>
<td style="text-align:left">Arc tangent of x (in radians)</td>
</tr>
<tr>
<td style="text-align:left">atanh x</td>
<td style="text-align:left">Hyperbolic arc tangent of x (in radians)</td>
</tr>
<tr>
<td style="text-align:left">cbrt x</td>
<td style="text-align:left">Cube root of x</td>
</tr>
<tr>
<td style="text-align:left">ceil x</td>
<td style="text-align:left">Ceiling of x — the smallest integer that’s >= x</td>
</tr>
<tr>
<td style="text-align:left">cos x</td>
<td style="text-align:left">Cosine of x (x is in radians)</td>
</tr>
<tr>
<td style="text-align:left">cosh x</td>
<td style="text-align:left">Hyperbolic cosine of x (x is in radians)</td>
</tr>
<tr>
<td style="text-align:left">exp x</td>
<td style="text-align:left">e^x (exponential/antilogarithm function with base e)</td>
</tr>
<tr>
<td style="text-align:left">expm1 x</td>
<td style="text-align:left">e^x - 1</td>
</tr>
<tr>
<td style="text-align:left">floor x</td>
<td style="text-align:left">Floor of x — the largest integer that’s <= x</td>
</tr>
<tr>
<td style="text-align:left">length x</td>
<td style="text-align:left">String length of x</td>
</tr>
<tr>
<td style="text-align:left">ln x</td>
<td style="text-align:left">Natural logarithm of x</td>
</tr>
<tr>
<td style="text-align:left">log x</td>
<td style="text-align:left">Natural logarithm of x (synonym for ln, not base-10)</td>
</tr>
<tr>
<td style="text-align:left">log10 x</td>
<td style="text-align:left">Base-10 logarithm of x</td>
</tr>
<tr>
<td style="text-align:left">log2 x</td>
<td style="text-align:left">Base-2 logarithm of x</td>
</tr>
<tr>
<td style="text-align:left">log1p x</td>
<td style="text-align:left">Natural logarithm of (1 + x)</td>
</tr>
<tr>
<td style="text-align:left">not x</td>
<td style="text-align:left">Logical NOT operator</td>
</tr>
<tr>
<td style="text-align:left">round x</td>
<td style="text-align:left">X, rounded to the nearest integer, using "grade-school rounding"</td>
</tr>
<tr>
<td style="text-align:left">sign x</td>
<td style="text-align:left">Sign of x (-1, 0, or 1 for negative, zero, or positive respectively)</td>
</tr>
<tr>
<td style="text-align:left">sin x</td>
<td style="text-align:left">Sine of x (x is in radians)</td>
</tr>
<tr>
<td style="text-align:left">sinh x</td>
<td style="text-align:left">Hyperbolic sine of x (x is in radians)</td>
</tr>
<tr>
<td style="text-align:left">sqrt x</td>
<td style="text-align:left">Square root of x. Result is NaN (Not a Number) if x is negative.</td>
</tr>
<tr>
<td style="text-align:left">tan x</td>
<td style="text-align:left">Tangent of x (x is in radians)</td>
</tr>
<tr>
<td style="text-align:left">tanh x</td>
<td style="text-align:left">Hyperbolic tangent of x (x is in radians)</td>
</tr>
<tr>
<td style="text-align:left">trunc x</td>
<td style="text-align:left">Integral part of a X, looks like floor(x) unless for negative number</td>
</tr>
</tbody>
</table>
<h4>Pre-defined functions</h4>
<table>
<thead>
<tr>
<th style="text-align:left">Function</th>
<th style="text-align:left">Description</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align:left">random(n)</td>
<td style="text-align:left">Get a random number in the range [0, n). If n is zero, or not provided, it defaults to 1.</td>
</tr>
<tr>
<td style="text-align:left">fac(n)</td>
<td style="text-align:left">n! (factorial of n: "n * (n-1) * (n-2) * … * 2 * 1") Deprecated. Use the ! operator instead.</td>
</tr>
<tr>
<td style="text-align:left">min(a,b,…)</td>
<td style="text-align:left">Get the smallest (minimum) number in the list.</td>
</tr>
<tr>
<td style="text-align:left">max(a,b,…)</td>
<td style="text-align:left">Get the largest (maximum) number in the list.</td>
</tr>
<tr>
<td style="text-align:left">hypot(a,b)</td>
<td style="text-align:left">Hypotenuse, i.e. the square root of the sum of squares of its arguments.</td>
</tr>
<tr>
<td style="text-align:left">pyt(a, b)</td>
<td style="text-align:left">Alias for hypot.</td>
</tr>
<tr>
<td style="text-align:left">pow(x, y)</td>
<td style="text-align:left">Equivalent to x^y. For consistency with JavaScript's Math object.</td>
</tr>
<tr>
<td style="text-align:left">atan2(y, x)</td>
<td style="text-align:left">Arc tangent of x/y. i.e. the angle between (0, 0) and (x, y) in radians.</td>
</tr>
<tr>
<td style="text-align:left">roundTo(x, n)</td>
<td style="text-align:left">Rounds x to n places after the decimal point.</td>
</tr>
<tr>
<td style="text-align:left">map(f, a)</td>
<td style="text-align:left">Array map: Pass each element of <code>a</code> the function <code>f</code>, and return an array of the results.</td>
</tr>
<tr>
<td style="text-align:left">fold(f, y, a)</td>
<td style="text-align:left">Array fold: Fold/reduce array <code>a</code> into a single value, <code>y</code> by setting <code>y = f(y, x, index)</code> for each element <code>x</code> of the array.</td>
</tr>
<tr>
<td style="text-align:left">filter(f, a)</td>
<td style="text-align:left">Array filter: Return an array containing only the values from <code>a</code> where <code>f(x, index)</code> is <code>true</code>.</td>
</tr>
<tr>
<td style="text-align:left">indexOf(x, a)</td>
<td style="text-align:left">Return the first index of string or array <code>a</code> matching the value <code>x</code>, or <code>-1</code> if not found.</td>
</tr>
<tr>
<td style="text-align:left">join(sep, a)</td>
<td style="text-align:left">Concatenate the elements of <code>a</code>, separated by <code>sep</code>.</td>
</tr>
<tr>
<td style="text-align:left">if(c, a, b)</td>
<td style="text-align:left">Function form of c ? a : b. Note: This always evaluates both <code>a</code> and <code>b</code>, regardless of whether <code>c</code> is <code>true</code> or not. Use <code>c ? a : b</code> instead if there are side effects, or if evaluating the branches could be expensive.</td>
</tr>
<tr>
<td style="text-align:left">when(case,value,case,value,defaultValue)</td>
<td style="text-align:left">条件语句</td>
</tr>
</tbody>
</table>
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